The closest example in the canon is when Ranma thought Akane was dumping
him for Shinnosuke (vol. 26). He was hurt, but not really angry; he
didn't cuss out Shin-boy or beat him up. (Of course, you could argue
that Ryoga is more of a known quantity than Shin-chan was, and Ranma
already had some hostility toward him.)

He also didn't harbor any thoughts of jumping into the arms of one of
the second-string fiancees (though that could have happened later on if
he hadn't realized his mistake). The translation I have has him planning
to go on a training trip, and he actually ended up staying with Akane
and fighting the eight-headed serpent.

The Ranma in this story didn't seem hurt at all. It's more like, "Akane
dumped me? Hah! Never liked her anyway! I'll just move on to good old
number two!" I don't see Ranma as a deep guy by any standards, but
c'mon, he can't be THAT shallow, can he?

It's my guess that Ranma would be thinking something like:

How long has Akane been sleeping with him?! I bet she has been porking that
pig from the time he started being P-Chan! THAT WAS MONTHS AGO!!!! THAT
SADISTIC LITTLE SL*T!!!! I bet she mallets me for fun knowing I love...
LOVED her enough to put up with it! If she thinks she can keep it up she has
another thing comeing!!!!! I'm going to stop this stupid engagement today,
I'm not marrying that bit*h!!!!!

Betrayal can invoke some power negative emotions.

Psycho Sam