Tough 1 -
The Volcano Somewhat challenging level to start off the rank, but it's quite open-ended. Even then, it's not easy to figure out how to get over the volcano in the level.
Tough 2 -
Once upon a Lemming Another nice 16-of-everything except for builders where you only have 1 level. I made the go around the long way happen way more often than it needs to, as I could had simply platformed up the gap at the far right.
Tough 3 -
Like a record Lemmy There's the other half from the song title by Dead or Alive. Again, nice concept of preventing the preplaced floater from dying to the needle traps with walkers, but way too excessive with the skill assignments for my liking. However, I understand this is where the title of the level comes into play.
Tough 4 -
NoW uSe MiNeR aNd ClImBeR Nice level that has a repeat later. There are also slowfreeze/radiation objects, although it's not possible to reach them here. Just there for decoration. These aren't actually used in the pack at all.
Tough 5 -
Where's Lemmy? Nice level featuring entrances with a separate set of preassigned skills from the preplaced lemming. The latter does most of the work, and then the ones from the hatch are used to disarm the traps to allow the preplaced lemming to safely exit with the rest.
Tough 7 -
Charge! Somewhat hard level. Fortunately the starting platform is very wide to allow you to get the solution down, but the high RR can be hard to manage. Also features the backwards builder trick to get over the final wall to the exit, which is a pretty subtle trick that can throw you off if you aren't aware of it.
Tough 8 -
One way and another Nice level, although here I used more than I needed to
Tough 9 -
Forgot me pickaxe! Not sure what the pickup is for, as I solved the level without needing to use it

Not a bad level, but this one can definitely benefit from making the hatch a preassigned climber/glider one, as then it wouldn't be as annoying. Then it would just reduce this level to a diggers puzzle.
Tough 10 -
How Shocking! Nice level. Hardest part is figuring out how to contain the crowd, as well as how to isolate another worker to finish the rest of the path after bombing the first one through the wooden pillar. Just barely realized the terrain spells out "Oh No"

Tough 11 -
Get me outta here! Nice near repeat, with the added challenge of some terrain overhang and an extra hatch to save.
Tough 12 -
Lemmy wants uppies! Nice concept with basher staircases via bashing and cancelling with walkers midstroke, although a little too repetitive for my liking.
Tough 13 -
Puzzle hero Nice 1-of-everything level, similar to the Mayhem 3 type, except you have a platformer in place of the digger. I was unaware of the trap in the water the first time I played the level.
Tough 14 -
I'll scout ahead! Nice short and somewhat easy level. I think it's possible to finish with a builder to spare here.
Tough 15 -
Ducka you head III Third level in the series. This time, you need to cancel building with bashers to avoid the fire traps. Probably a bit harder than the previous one in that you have a small platform to work with that you start on.
Tough 16 -
This erosion Nice hard level, but way too much bombing for my liking.
Tough 17 -
Just dig faster! Nice short level, but it can be very fiddly to execute. Can also be very frustrating due to the time limit. I pretty much finished at the very last possible moment when time ran out, although I think that can easily be remedied by doing some more cancelling with the digger that was left.
Tough 18 -
Faithful Guards Nice level where you need to eliminate the zombies by the exit via a worker that takes a separate path from the crowd. Figuring out how to do this can be challenging.
Tough 19 -
Spread out, men! Near repeat of a level earlier in the rank. I really like this one! That was especially clever with bashing and then mining before he breaks through the wall in order to isolate a lemming who floats down into the pit on the right to build over the traps before the other two arrive.
Tough 20 -
The dreaded fetch quest Third boss level of the pack. A bit harder than the previous ones, but it's still not too hard. A bit dragged out IMO