Any opponent will find it difficult to beat him.

Student or Learner
Hi
Mr X is a talented boxer and has a black belt in Brazilian jiu-jitsu. He was/is a handful for any opponent.
What does it mean he is a handful for any opponent?
Any opponent will find it difficult to beat him.
However, that's not how I'm used to seeing this idiom used. The usage I'm personally familiar with is for rambunctious children. "Ah yes. Little Peter. He's quite a handful. Last week he put a frog in his sister's bed. This week, he painted the seat of his teacher's chair."
What do others think?
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
I agree that Barb's is the more common usage but if I saw it used in the context of a sportsperson, I would have no trouble understanding what was meant.
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