This is an interesting comment. If there is high definition video available that will provide the examples needed what difference does it make if it is from a high school or college game?
Watching video of excessive hits, at any level, with instructional advice on what about the hit may have been problematic, can be helpful, but they are NOT the hit that you may be looking at and have to determine is legal, or illegal. It is ABSOLUTE, no two plays are exactly alike.
Understanding the rule, it's purpose, it's history, it's objective and being in the proper position to thoroughly see, and focus on, what happened, including the set up and lead up to the contact is what helps make the right call. It's not easy, or guaranteed, to factor in intent and purpose, but that's often part of the evaluation process.
EXCESS:" that which passes the ordinary, reasonable or required limit" is a judgment call related to what you are seeing in the specific situation you are looking at. It is unique to the play you are looking at, may be different than all the plays you've seen before, or will see after. (From the NFHS POE, "The game official must draw distinction between contact necessary to make a legal block or tackle and that which targets a defenseless player".
It's an individual judgment and decision specific to the contact you are looking at, and what's happened before (live, or what may have been seen on a video(s) of some previous play(s)) isn't going to make the call. As with ANY foul, it there is ANY doubt that it was, then it wasn't, and we need to be sure of that difference and be willing to make the call and stand by it.
The clear cut calls, either way, are usually easy. It's those borderline, bang bang calls you can be sure will bring challenge and complaint, and what happened before, somewhere else, doesn't take the monkey off your back alone, then and there.