- That One Achievement:
- In terms of early-game achievements, "Zero Deaths" is one of the most difficult and time-consuming to obtain before you get Infinity Dimensions. You need to complete a challenge without any Dimension Shifts, boosts, or Antimatter Galaxies, and the only Challenge where this is remotely possible is Challenge 3, where the first dimension grows in power at an exponential but slow rate. This will take over 20 hours without any Infinity Dimensions, which you only obtain in the mid-game. This eventually got pushed down to become a mid-game achievement.
- The mid-game achievement "How the Antitables Have Turned" can be missable thanks to how it works: You need to have your 8th dimension multiplier higher than your 7th, your 7th higher than your 6th, 6th higher than 5th, 5th higher than 4th, etc. This is especially tricky once you get certain upgrades that improve your 1st dimension multiplier, causing it to become too big for the rest to get above it. As such, it was pushed up to become an early-game achievement, where it is indeed easier to obtain early-game.
- In the late-game, there is "Long lasting relationship" which requires you to produce more Infinity Power per second than your Infinity Power for 60 consecutive seconds. It is hard because Infinity Dimensions don't produce Infinity Points, and maxing out them makes your Infinity Power production only briefly exceed your Infinity Power. To get the achievement, you have to manually buy ID1s one at a time at a certain rate for 60 seconds, and even if you mess up once, the timer starts over. However, there is a Time Study, which makes this much easier, and allowing you to get it automatically without any strategy eventually.
- That One Level: Some Challenges are far tougher than normal when initially unlocked. Of course, once you have obtained enough IP, skills, or achievements, they turn into a breeze.
- Challenge 9 when initially unlocked requires you to do things manually, because whenever you buy 10 of a dimension or tickspeed, everything else of equal cost will increase to its next cost step. This can make things unwinnable and thus have to force a reset to retry.
- Likewise, Infinity Challenge 5 when initially unlocked requires good micromanagement. In addition to having Challenge 9's restriction, when buying dimensions 1-4, everything with costs smaller or equal increases, and when buying dimensions 5-8, everything with costs bigger or equal increases. This means that you can make things impossible until you reset if Dimension 8's cost gets too high. When buying tickspeed, everything with the same cost increases. Like regular Challenge 9, this requires very careful planning.
YMMV / Antimatter Dimensions