I do think about how exactly the july accident happened in trimax... Like Knives clearly influenced Vash to do it but he also clearly expected something different to happen (because the blast meant he was caught in it and all but died). And we know the independent plants can influence emotions but I don't think anything ever suggested they could straight up rule another's movements? (except Vash slowed down the heart of that one plant and Knives took over Domina but the second was due to mindmeld and the first was probably the same? (Though most likely just not planned out enough since that happened in trigun and not trimax) But Knives can't meld with Vash because when he tried he was immediately swallowed up-)
Like I guess it's up to each person to come to their own conclusion but with how Knives says it's supposed to be like a relief or release, I kinda do like the idea that what happened was he influenced Vash to stop repressing his feelings - which was, more than any other, rage.
Ok wait wait so we do get Vash doing this thing overtaken by another emotion - grief/sadness at Wolfwood's death - and it's completely nondestructive to his surroundings, but causes a loud booming sound like thunder.
What can also be concluded is that the feeling Knives' is repressing isn't anger (duh, it's fear. Obviously fear.) even if he might have thought/told himself it was.
I realised we do actually see what the likely fear-response release that Knives expected was too
(and this part could be Wolfwood just making it up using known powers to make sure Vash agrees to come back, but I figure it's true probably)