Lots of good advice & I will add my 2 cents... Get the calf to trust you & don't ever let a calf get it's bluff in on you... cattle can tell when you are scared of them & they can play off it. There are way too many tricks, methods & things that you can do to protect yourself while breaking/gentling a calf (like a broom stick/show stick... put it in an alley or squeeze chute & brush it... spray with a water hose... tie cans on it's tail... hang several bags or cans on each side of it... tie to a donkey... etc... etc...). Take your time with the calf & whatever you do, when it kicks or acts up, don't stop... if you think that you may get hurt, you need to immediately try something different where you can't get hurt (like get a broom or a show stick or a water hose), but whatever you do, do not let up. 1st thing I do is break with a broom stick/show stick in a small pen. If you stop when the calf kicks or acts up, the calf will quickly realize that when it kicks, you will stop & it may get worse quickly. Kinda like not letting one go when breaking it to lead... you don't have to hang on with all your might & let it drag you, just have a long enough rope & a small enough pen where the calf can't get away in the 1st place. Think smart, stay safe, don't let up, & get the calf to trust you.
FWIW, when all else has failed... a good soaking spray with the water hose will help as much as anything. I've broken lots of bad kickers (Chi - Limi - Beefalo - Brahman influence cattle) with a spray nozzle & water. Just make sure that you have plenty of time to spend when you start rinsing, because to do it right, you will want to rinse her until she completely stops and/or wears herself out. And be sure to move the water around... don't just spend all your time only spraying the rear legs. I like it better when you get them completely soaked, but if you don't want to do that, at least move back & forth switching between the front & the rear legs & inside & outside...also spend equal time on the right side & left side.
RE ace... sometimes it helps... sometimes it makes it worse. I've used beer in the feed (I sometimes have soaked beet pulp in it) to calm calves too, but like ace, it can occasionally cause some to act up worse. Never used it, but I would think that melatonin would be much better.