If you see an alpha rex please be careful, they are unbelievably scarier than a normal rex keeping up with a spinosaur and not getting phased by anything we threw at it. Rip Zeus, level 113, the rex was 25.
This is tge least threatening creature in the game once you hit lv 10. Craft a bow and some arrows, shoot it and kite. If it is gaining on you, run past a herbivore, it will lose aggro almost instantly. Keep shooting that sweet sweet early exp and possibly early metal tools.