Biggest acheivement is probably the FNAF series considering its the most famous and people always want more of that. Also beating that game is a pretty big acheivement considering how repetitive it is. My personal favorite out of these would be prop hunt tho. (Also you forgot to mention Drunk Minecraft up there^. You should check it out if you haven't, it's one of his best if not the best series.)

Depending on what an "achievement" is. His most viewed videos can be seen here: https://socialblade.com/youtube/user/markipliergame/videos/mostviewed. Which are mostly FNaF, yes. He was one of the first to make videos about them, and one of few to clear each of them on highest difficulty. But he has other great accomplishes, like moving to Los Angeles, getting an editing team, raising crazy sums for charity, going on a tour to Europe, etc.

Thx both of you. I was arguing with my brother on this and he kept saying that other games were more viewed and all. Last time, I watched his Fran bow series, and his prop hunt vid series. So I wouldn’t know. Thx very much ^~^