From this manga panel:
I'm having trouble with understanding「ヘマッたことが多すぎて」
I guess this to be "The messed up things (I did) are too many"
I think ヘマ = blunder, and こと = generic "thing", but I don't understand the ッた between them.
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Sign up to join this communityIt's the past form of a slangy godan verb ヘマる.
e.g. やる → やった Likewise, へまる → へまった