Infinity expert if you want a real challenge, mabe project ozone 2 titan mode, like a combination of expert mode hqm and skyblock
Crash Landing is old but still hard as always, specially on hardcore mode ;p TRY TO NOT DEHYDRATE!!!!
Except in galactic science it's way too easy to get more air. The only real danger is if you forget your spare tanks and go out too far.
CrashLanding isn't very hard once you make a hyper sieve and know about the trick for easy water. Just need a few auto crafters and a bunch of camel packs. -V