Mutilation 10: Twisted Track -  This is somehow a hard level for me. A digger and a blocker saved, so not intended I guess?
Mutilation 14: Started From The Bottom... - Similar than my previous solution, but now I needed to use the bomber.
Decimation 2: The Winning Edge - This feels intended. The structures on the right did matter after all!
Decimation 10: Across The Sky - Okay, now I had to juggle with three of the cloners. One bomber and thus an extra guy saved.
Decimation 12: A Lot Of Lemming Going On Here - My solution barely works, basher+platformer+builder placement is pixel precise in its height, and the time limit is just enough with this crowd cycle. An extra lemming saved.
Obliteration 3: Lemming On A Prayer - Okay, this I had spoiled myself because I solved it already via backroute and then read the hint. :p

Obliteration 4: White Noise - I am not even close on this one yet. I thought my best attempt was crossing the digger and basher but I don't have the means to turn the worker lemming around at the right side of the level to build a bridge over the water for the crowd.
Obliteration 9: Aquadynamics - Skipped at first and solved after Obliteration 10-12, when I realized that I could actually take both lemmings over the one-way wall at the right.
Obliteration 10: Dirty Joke - The one-way stacker was the key element in the middle of the level.
Obliteration 11: Bending the Rules - This is most probably a backroute.
Obliteration 12: The Golden Rule of Lem - A ferocious looking level, but really fun to play! It's always a good feeling when one plays a level that seems huge but it turns out to be a lot more accessible than one would think at first.

Decimation 11: Caving Under Pressure -  My approach is brute-forceish so I really think there's another route which is intended. I didn't work on my way with the crowd control yet before finding the correct digger-builder placement for the blocker release in that mound (I tried it from the both sides of the blocker, both the worker lemming and a crowd lemming, both digger facing at the blocker or away from blocker).
Decimation 15: The Longest Minute - This is a failure by one frame, that one guy eagerly goes to the void. I'd think that my skill placements are correct. I also did this level so that the last entering lemming was already hopping to the exit but the timer went to zero.
Obliteration 1: A Severe Case of Lemmingitis - A breather here, a really straightforward level.
Obliteration 2: Good Lemmings Die Young - A good and well-placed level.
Obliteration 3: Lemming On A Prayer - This one I suspect backrouting.

Mutilation 4: Jump Scene - Basher saved. Also this is clearly the easiest level in the pack.
Mutilation 14: Started From The Bottom - Climber and bomber saved.

Decimation 3: Lemming Semantics - A nice map, solved immediately though, so should be in the first half of Mutilation probably.
Decimation 4: Oh Blast... - Same here, though again this nice trick of yours from Dead is the New Black and Odyssey.

Decimation levels 1, 3, 4 and 6 are solved as fast as Mutilation levels, so there's no apparent difficulty gap there in my opinion. Mutilation has a nice difficulty curve, though especially levels 13 and 15 are harder than this first half of Decimation, probably on purpose.

Decimation 8: Mission: Difficult - The good old stepover turnaround saved me after trying the super annoying pixel precise fatal fall for non-glider climber, grr!
Decimation 10: Across The Sky - I didn't use cloners (for other than reaching the save requirement).
Decimation 12: A Lot Of Lemming Going On Here - Floater and extra lemming saved.

My solutions for both Decimation 11: Caving Under Pressure and Decimation 15: The Longest Minute fail by single pixel or frame, even in different attempts, so I'm now quite worn out by these two...

Fluffy 10: Cell Network - It's a puzzle! Asymmetric solution in a symmetric level, oh yeah.

Coarse 5: Tactical Drops - An original and clever no-skill level, and not too frustrating.

Spiky 5: Mushroom Rock Road - I didn't solve this before, quite a solution right there! Probably not the intended one.
Spiky 7: Worker Segregation - I didn't solve this before, the key was to realize that a glider survives the drop from left to right.
Spiky 14: Hot Plate - I didn't solve this before, it's great!
Spiky 20: Scenic Route - I didn't solve this before, the time limit is tight, yeah.

Sharp 3: Ground Zero - I had to re-solve this due to radiation objects changing to fire traps, the same luck-relied beginning is there, I changed builder to a platformer at the end.
Sharp 4: Nom Nom Nom - I didn't solve this before. No idea why it took so long from me, the solution wasn't that complex in the end.
Sharp 5: Not Gonna Fly - I didn't solve this before. I didn't like the luck-based grindy timing solution that I found, I suspect there's a different one.
Sharp 6: It's Not Meant To Bee - I didn't solve this before, it's great!
Sharp 8: Roster Shuffle - I didn't solve this before. The beginning has this common mind game: you can let that one lemming die and use builder, which is slower than platformer. Climber-holding pit looks very natural in the starting area.
Sharp 9: Lem 51 - I didn't solve this before, it was a bit pain to execute the timing.
Sharp 10: Sweet Tooth - I had to re-solve this for whatever reason, my solution is pretty much the same than it always was.
Sharp 12: Drawing Dead - I didn't solve this before, the main trick is tremendous.
Sharp 16: The Lemming Mangler - I didn't solve this before. This is a rare level I think I've somehow got spoiled, not sure from where (a YouTube video thumbnail probably).
Sharp 17: Broken Arrow - I didn't solve this before, but got the main details already back then, executed now just a bit more efficiently. Tough timing there.