I agree with Cherie. I don't know if I would characterize him as a spoiled horse, but I don't have the no-nonsense, work-a-day, trained hundreds kind of background that she does. So, listen to what she says.
My own trainer phrases it like this:
Your horse has this all inside of him, so do you want it to come out now, or on the trail, while you are on top of him?
That means, that his fear reaction to the whip is inside of him, the tension is there, the anxiety, and working with him in a way that avoids making that come out means that you will be riding out on a horse with that problem inside of him, maybe only masked by him having learned to stand still , suck it up , and "take it " when a whip is put on him.
So, let's say you work a lot on having him just stand still while you put the whip on and off, within his range of tolerance. You get to the point where he will stand still and let you do this, But, as soon as he gets moving, he explodes. So, the problem is still inside of him.
His exploding is an opportunity, not something to avoid. Its the beginning of where he can release his fear. If you stop there, you leave him with the fear. You must stay with him, HELP him get past it by remembering exactly what you are asking for and not accepting anything else.
So, if you are asking him to step forward, he explodes, backs up or tries to flee, you have to shut that down!, get him to look at you with both eyes for a bit, and ask him to step forward.
Even while he is struggling around, backing up, maybe rearing up a bit, trying to go the wrong way, you must not be deflected from continuing to ask , with the rope, to go where you are asking.
Without seeing exactly how you are trying to lunge, it's hard to give specific pointers on how to get better results, and it is no doubt very hard to do with a very strong and explosive horse on the line. (get a rope halter and use a 12 to 15 foot line). But I wanted to share with that way of thinking about this kind of problem to see if it might help you approach your horse differently.