I thought I'd rank the levels from the Tomb Raider Legend Trilogy favorite to least.
18: Mediterranean Sea (Underworld)
It begins with a massive underwater stage. Though you can't drown here, you do have to search for two axles. Controls aren't super awkward but the second one is in another structure I spent a while searching for. Inside Niflheim, the area is dull and a bit confusing at times, especially trying to figure out how to get to where you need to kill the kraken. Then when it gets to the combat on Amanda's boat, you realize just how much easier it is to die than in the previous games. And it ends with escaping from the sinking boat, though I think it's not timed or anything.
And to add insult to injury, they unavoidably stick Lara in a "fanservice-y" outfit for this. They don't even let you choose like in Arctic Sea. I love how Lara is USUALLY very attractive without being too "fanservice-y" so why the change?
This is the only one I actively dislike.
17: Coastal Thailand (Underworld)
I don't dislike the level, really. It is beautiful aside from the spiders, and both this and the outfits returning to Lara's usual style are a breath of fresh air from Mediterranean Sea. And there are plenty of Tomb Raider style puzzles and obstacle courses.
This only gets this low because of that one confusing room with lots of Naga fights that are a bit difficult given your low health. Other than that it's pretty good.
16: Croft Manor (Underworld)
This is a bit of a breather level after the first two. It's not particularly difficult. However, it is a bit dark and plain compared to other levels.
15: Nepal (Legend)
Lots of typical Tomb Raider style obstacle courses, though some can take a few tries. Despite its low placement I don't dislike it, I just like other levels more.
14: Peru (Legend)
Mostly straightforward level, and kind of a cool puzzle at the end even if took me a while to figure out. It gained some points for the driving stage which is kinda fun, but lost a few points for the flashback sequence, which, while not long, isn't quite as fun as the rest.
13: Natla's Mines (Anniversary)
It can kinda be a fun final stage for Anniversary, but a few bits can be annoying, mostly the battles especially as you ascend the long shaft which many players consider That One Level. Intro is a bit dull but not really annoying. Kinda fun quick time fights with Natla's minions, and more of those classic Tomb Raider jumps. And of course you get to fight Natla herself at the end.
12: Southern Mexico (Underworld)
As Tomb Raider Underworld levels go, this one's not really bad. The rain setting, and getting the jaguar heads and activating the calendars are a pretty fun puzzle, and while you are timed getting into Xibalba, it is manageable if you're prepared, and the song that plays is quite intense. Xibalba itself is pretty cool (aside from the giant spiders), the puzzles are pretty straightforward and the trap rooms aren't that tough.
The reason this isn't higher and I was a bit iffy about putting it higher than the last three is because of the eitr room, which many had to check a walkthrough for how to do right and gave me lots of frustration. All those Thralls must have been alternate Laras that fell into the eitr every time I screwed up.
11: Jan Mayen Island (Underworld)
This is where Underworld starts to get good. It begins with riding a motorcycle down a spiral path, then an obstacle course involving a large spinning platform, which is really fun and makes you feel like you're playing Anniversary or Legend again. The labyrinth (which, while called Valhalla, seems more like what Niflheim is) seems confusing at first but actually there is a very simple path to the final room, and if you know what to do it's a pretty fun obstacle course to Thor's Hammer.
10: Bolivia (Legend)
Again, pretty straightforward level. Beautiful level outside, the introduction to the Legend Trilogy's mechanics and my introduction to the series. The tomb was a bit dark but you have your light, and the puzzles and obstacle course are kinda fun.
Also of note, the final boss battle also takes place in the last area of the level, and as it is more of a battle than a stage I won't list it separately. Pretty straightforward battle considering you're using Excalibur.
9: Arctic Sea (Underworld)
It begins with another underwater stage but this isn't as annoying as Mediterranean Sea. Not just coz you can choose a less "fanservice-y" for Lara this time, but also finding the items you need is pretty easy. Once you enter Helheim it gets pretty fun. There is a bit of an obstacle course, a hallway full of Thralls, a very significant cutscene, and then the "final boss" is the ultimate obstacle course, which can be a bit confusing at first but if you know what to do, it is fun, and, DLC aside, ends with Natla's glorious death, even if you don't get to actually fight her yourself this time.
8: Peru (Anniversary)
A plain, straightforward level. But not really boring. It's still an ancient ruin and has plenty of those classic Tomb Raider obstacles. The waterfall room and both rooms where you open a door from the left and right is pretty cool, you get your introduction to Anniversary specific mechanics, there's a boss fight with a T-Rex, and Qualopec's tomb, while not particularly fancy, is still all right. And of course there is an Indiana Jones reference with the boulder.
7: Kazakhstan (Legend)
I thought I didn't like this level at first (I think due to winter setting) but it's grown on me a bit. The outdoor stuff isn't actually that long if you know where to go, then another driving stage which is very long but can be fun, ending with you driving your motorcycle onto a train. Then the actual Soviet facility, which is modern but doubles as a tomb due to scientists that froze to death in the 50's, is full of the classic Tomb Raider obstacles and such, and you get to operate a Tesla coil. The boss is kinda annoying though.
6: Japan (Legend)
This is kinda a departure from other Tomb Raider levels in that it is not a tomb, but a Yakuza base. But the Japan setting is pretty cool, and the soundtracks, and the fact that you're fighting gangsters, and Yakuza at that, and come out victorious. There are still some climbing obstacles outside, and some kinda cool puzzles inside, and the boss fight is kinda fun too.
I'm not sure whether those are meant to be Modesty Shorts under Lara's torn dress here; if not, then she's a bit "fanservice-y" here too, but I can look past that.
5: Ghana (Legend)
Begins with an awesome swan dive into the water, then more ancient ruins and death traps, and more climbing obstacles. This is a prime example of these tombs in Legend, and Lara's love for death traps. Among them is another Indiana Jones boulder. You get to fight Rutland at the end, which can be a bit annoying but manageable.
4: Greece (Anniversary)
One of the most memorable levels of the franchise. St. Francis Folly is pretty long and can be a bit confusing to get to all the switches and doors but other than that, the god challenge rooms can be fun (and yes, another Indiana Jones boulder in the Atlas room), though the game doesn't tell you how to do the grapple jump to the side in the Damocles room. The Coliseum is a cool setting in general but a bit plain and short. Midas room is pretty iconic; aside from the Sa'luk death scene, the first and third lead bar rooms are pretty fun.
The Tomb of Tihocan can be a bit confusing at first glance, but once you know what to do it's not so bad, and the boss battle is a bit crazy but not overly difficult IMO, if you know what to do.
3: England (Legend)
It begins as a tourist attraction that is clearly a fake King Arthur's tomb, during which you get an entertaining comment from Alister about Excalibur and the Sword in the Stone being two separate swords. Then behind a brick wall you drive a forklift into the real King Arthur's tomb, and after the forklift falls you get another entertaining comment from Zip. From here it's more obstacles and death traps typical of a Tomb Raider game, and then you enter a giant room, where after some more fun obstacles and kind of a clever puzzle you get the last Excalibur fragment from King Arthur's tomb itself.
The boss fight with the sea serpent (who you ominously hear while first entering the room but don't see until after getting the sword fragment) might be a bit Guide Dang It but if you know what to do it's not super difficult, though there is some backtracking involved from here.
2: Egypt (Anniversary)
This level practically defines Tomb Raider levels as I see them. Climbing obstacles, some puzzles, a bit of swimming stages, and occasional combat with enemies. There are some entertaining moments listening to the rat theme when rats attack, mainly in the hall to the giant water room. A few bits of it can be frustrating and take a few tries, but not overly frustrating. It's fun seeing which room is next, and most of them are fun enough. And of course ancient Egyptian settings are always cool.
Still not perfect though. There is a beginner's trap in one room where if you pull a switch that is completely optional and gives no rewards, circular blade death traps activate making the room difficult, but it's easy if you just don't get the switch. And there is one Guide Dang It part at the beginning of Part 3, of rotating pillars a certain way which could softlock you if you do it wrong, but if you know what to do, it's an easy solution.
1: Andaman Sea (Underworld)
This level is not Tomb Raider-esque at all, it's very short, and it is basically a replay of the Amanda's boat section of my least favorite level. But this time you have Thor's Hammer. It is so much fun walking through the rain and smiting Amanda's minions with Thor's Hammer and sometimes sending them flying over the edge. More than anything it seems a level to get you used to Thor's Hammer, and it makes everything leading up to it worth it.