Yes, 12Raph gets angry a lot and yes he wants 'revenge' the most out of the turtles (like when he wouldn't let the guy in turtle temper go). So I see, that Splinter might see shredder in him.
However, one thing that Raph has to get more credit for is that his anger dissolves fast.
In mutant gangland, Raph snapped and quits the team for the n-thed time. As Donnie comes to him the very same night, and Raph isn't ready to accept his apology yet, Don's honestly surprised! And when he's in danger seconds later, ofc Raph's ready to fight for him - no hesitation cuz duh!
And, sure maybe Shredder too was so fast to forgive a long time ago before all that happened but somehow I doubt it.
If Raph's outburst and hotheaded actions at the age of 15+ means he says something impulsive, kicks some trashcans, calms down and apologizes only hours later - I think he's on his way to not become even remotely close to Mr. ''The love of my life has taken the strike that was meant for my brother, I should seek him and hunt him down for the rest of our liv- holy shit is that something with his logo? I should move to a different country in hopes of finding and killing him without having any other clue'