How do you beat him? I've tried and keep dieing or fall, and when you beat him do you beat the mission or do you have to do more?

if you want to beat red follow these tips:
1: get X and his armor
2: fight red with X and Axl.
3: use sniper missile with Axl until it runs out then use it with X until it runs out then use X's charge shot.
4: sorry but it's your fault if you fall.
5: get the energy tanks.
6: (note if you use X and you get hit by Red's counter you will still be standing)
7: good luck and happykilling red

shoot 'm

Use a ranged character. Preferably X with armor. If you fall, it is pretty much your fault. Just be careful.