Pain, suffering, practice, and more pain. Had to beat the whole game without running out of lives. Everything was practice for that. The winning run had me deathless until the second to last world, with 5 lives remaining.
1CC, becausde this was the only way to reach the final levels in the first place. Blind stage 5 and 6 once I realized being speedy was the best option.
After grinding the story mode enough times, spent 2 hours to clear extra with all 3 characters, learning routing and getting 999+ dyes in a run. Achievements gotten.
All achievements gotten. 3 hours for Cancer Speed, the rest of the time was spent grinding attempts in order to get powerful enough to... no-hit a specific boss.
Still missing wins with a few characters but that isn't an achievement.
First easy mode with no upgrades, then hard run clear, then hard run with 50k gold. Then finally the challenges. Did not have to grind because I could simply do challenge 4 again.
While grinding for Version B medals, got the 2-ALL with Sadahl, the one character I was missing his ending and better than Loop at certaing things. Then grinded a bit more and got the medals.
Beat the game with a continue, then again (both on hard) with 1.5M points. Then grinded the start of level 5 for the 10k kills, killing my character to force end the run because it doesn't save otherwise until the end of the level.