The Melter’s whole gimmick is that his flames can melt away at you, but it won’t mean much when you consider that Vegeta’s aura can block any attack that is thrown his way. Vegeta can easily bust the planet as well to avoid even having to bother dodging/blocking. The Melter just isn’t in the same league as this Saiyan and so he never had a chance from the start. One attack will end this. Vegeta wins.