I'm looking for a noun.

[peppy_man]

Is there any noun for a person who always trips others up,
just trying to show his/her own presence?
Thank you in advance.

[Jenny 7]

An 'attention-seeker' is the noun that comes to mind. Though I don't know that he'd necessarily trip you up, he'd always want to be noticed.

[hobbes]

Possibly "smart-alec" (polite) or "smart-arse" (rude).

This person uses their personal knowledge to try to impress or make others look less intellegent. It is nearly always unwanted & done to show they have superior intelect, and I suppose could be done to lay 'traps'.

[peppy_man]

Jenny7, hobbes, thank you for your responses.
Is there any expression for a person who only criticizes others
without putting forward any constructive idea?