IT can only be harmed by silver if the wielder believes it will be. It was very heavily implied that the losers club was somehow supernatural, and their uniquely strong imaginations were the only way to harm it. How would Violator harm it...and moreover, what is Violator most afraid of?
IT's nemesis vomited up the universe whole, that's some power.
Pennywise from what i can see only takes form of the persons fear but can he actually use that power?
But i dont think that he would have to much trouble beating pennywise because isnt it whatever you believe can hurt him will and they believed he could be beaten with silver rocks like the werewolf but they had to kill him twice how did he come back? Did it ever explain that? If the violator thinks that his power is stronger wont it be stronger?
it was not harmed because it was silver, but rather because it was a projectile shot into its delicate vital area.
the reason the clown "died" was because the kids stood up to it.
thats why the "battery acid" a.k.a. asthma breather also harmed it.
they were battling a telepathic projection of their fears, so once they
did not fear it, it was powerless. the actual incarnation of 'it', however was not, as we see the "battery acid" had no effect and the silver bounced off its head.
so really there are only two possible battlefieds:
1-it attacks violator through telepathic projection, upon which violator would probably laugh in his face---stalemate
2-violator goes to it's lair and attacks the physical incarnation, killing it instantly
however, there is the unlikely: that the physical it's 'dead lights' would have the same hyponotic effect on violator, upon which it might stand a chance of winning.