I’ll claim it was evidence he was seething and had to say the last word so someone would hear it lol. They can claim they’ve won to others and lie to themselves as much as they want, but at that moment when you walk away and they can’t reply, you both know who took control of the situation

Edit// It can also be even funnier if you don’t block them, just say goodbye in the final message, and then never reply whatever they write. Then you get to see their final attempt to say the last word, but they have to wonder did you not care enough to even block them, and can’t be sure did you ever read it. This apparently takes some weird form of self control though, so blocking might be better for most people (and it depends on the platform can it work)