I don't think a movie with dinosaurs can get any more epic than that

Who do you guys/gals think would win? The Indomitable King or the Tyrant Lizard King?

At the end of the movie, Owen re-establishes his bond with the raptors before the Indominus reappears. The raptors attack the Indominus, but three of the four are killed. Claire lures the park's Tyrannosaurus rex into a battle with the Indominus. The two dinosaurs fight, with the Indominus gaining the upper hand until Blue, the lone surviving raptor, joins the battle. Overwhelmed, the Indominus is backed up to the lagoon, where the Mosasaurus leaps out and drags it underwater. The T. rex retreats, followed by Blue, who turns to acknowledge Owen before leaving. (taken from wikipedia)

It has been confirmed that this T-Rex is the same as the one in the first movie.

I do not think the T-Rex befriended Blue.

I think that the T-Rex is afraid of Raptors. Seeing how well Blue fought the Indominus Rex, and being wounded in the first movie, around the neck by raptors, I would say that Rexy came very close to dying, and was since very carefull around them.

Let's not forget he/she(?) is also very old. (at least 22 years). Histologic analysis of Tyrannosaurus rex say that aprox 30 years of age may have been close to the maximum for the species.

They are also very territorial, seeing the Indominus as a threat, not Blue, thus ignoring it.

After fighting the Indominus, coming very close to losing, fighting a very agile raptor would have been a death sentence.

TL;DR: Rexy was afraid of Blue.

Feel free to chime in.