In the comics, Grimlock isn't a dummy like the cartoon. He's a brutal, savage, super smart guy who just can't talk right because his circuits were screwed with. Optimus has had to put him in his place several times and the Prime always wins.
Pretty much all comic book versions of Prime are more powerful then Grimlock. The combined Dinobots couldn't even handle a badly damaged Megatron.
Earthforce is an exception. Grimlock fought Power Master Prime to a draw, and handled Shockwave a lot easier then in mainstream comics. Too bad Earthforce is not considered canon.
As far as the toon goes, Dinobots beast modes were indestructible. The only one who beat them in dino mode is Wheeljack, who's shoulder mounted gun was kind of a plot device in that it depowers its target.
Prime should lose, unless he could goad Grimlock into assuming robot mode, or trap him somehow.
__________________ What CDTM believes;
Never let anyone else define you. Don't be a jerk just to be a jerk, but if you are expressing your true inner feelings and beliefs, or at least trying to express that inner child, and everyone gets pissed off about it, never NEVER apologize for it. Let them think what they want, let them define you in their narrow little minds while they suppress every last piece of them just to keep a friend that never liked them for themselves in the first place.
Never let anyone else define you. Don't be a jerk just to be a jerk, but if you are expressing your true inner feelings and beliefs, or at least trying to express that inner child, and everyone gets pissed off about it, never NEVER apologize for it. Let them think what they want, let them define you in their narrow little minds while they suppress every last piece of them just to keep a friend that never liked them for themselves in the first place.