Just have many friends from clubs and you'll eventually get 100 if you stay on chess.com long enough, but if you want to speed up the process, then there's also forum threads with "trophy exchange" where you and others give each other trophies to help with achievements like that.
The hardest achievement
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Award magnet. For a random person to give you 100 trophies, is quite hard, unless, you use a friend or are a famous youtuber