Used to be the most overpowered Dino in the game, even at a low level, but now, after several stat decreases, if you tame a low level (under level 100) any decent bred Rex will kill it, so don't be too excited when you get one.
On mobile, they rage but they don't actually att ak you or your tames. I live below a cliff and my giga fell of and her eyes glowed but she didn't do anything.