It's not a scene that was ever going to be written. But with that out of the way...

I think he wouldn't have. Much of Belkar's anger stemmed from survivor's guilt and feeling indebted to Durkon in particular. His rage towards Vamp Durkon was due to the perceived affront to Durkon. I think even in his rage Belkar would be able to realize harming Kudzu would have rendered it all meaningless.

It's irrelevant, though. Durkon couldn't make a path to his undead heart without also getting Kudzu out of the way.