Is there a game that made you start the hunt ?

As we all know, we're part of a pipeline, we started playing game casually when one day, one of them made you think "hmm.. Might as well" and you completed your first 100%,probably another one etc..

Until one day, you start to realize that feeling of completionism is actually... Really nice, and you started hunting, maybe to fill that feeling, to fill a gap in your life or just for your ego, your profile or to complete your backlog

What was the game that caused it for you ?