If you had it in you to hurt someone, you would not announce it, unless you were stupid. Picking fights is useless, and "beating" people in real life is generally a pain in the ass with tedious legal repercussions, win or lose.
Rather than making threats on a forum you should simply plan for a week off of work and aspire to kill him during that time instead, if you feel that way, that would allow you a situation to "prove yourself" as your threats indicate you desire to, at least to yourself and potentially them before they die.
This begins with not announcing your intent.
But guess why normal people don't do this (or threaten to)? It's because they know they wouldn't. It isn't because you are tougher than them: for beatings, legal and very potent social repercussions are an annoying enough deterrent. As for death, it's because it doesn't offer much. And real death is generally very fast and unsatisfying. Most people aren't true sadists, so torture until death is out for them (and probably you too). So neither beatings or murder in this situation are likely to provide you a positive net happiness. Yeah?
Why make threats you will not follow through with? Why make threats that actually disable you from following through to begin with?
You would help your image a great deal if you did not make empty threats.