Red is probably up there with Hyenard as one of the hardest bosses in X7. He's definitely harder than Sigma.

I used the crash on him. I don't know what it is called in X7 or what boss gives it to you but it is similar to the giga crash from X2. I know one of the bosses gives it to you.

Just get right up in his face and use the crash. If you are using Axl, then equip that weapon and he will get a bazooka with infinite and very powerful shots. Just hit Red with these bazooka shots. I think he's weak to this crash weapon.

If you are using X to do the crash on him, do not do it during the first half of the battle. He is very easy during the first part of the battle and you don't want to waste your crashes on him until he's almost dead. If you do you will run out and be really screwed when he gets harder.

Mostly though I'd stick with Axl and the bazooka weapon though.