boss tricks: helios
Defeat Helios with one hyper mode following this method. Go hyper and start charging a shot while moving almost right under him. Just before it charges fully, release it to make him take the brunt of the attack. This will trigger the cutscene if he takes enough damage, but keep pressing A just in case you need a few uncharged shots afterward.
Helios will now come down to ground level and prepare his slashing attack. Hit him with a fully charged shot to remove a third of his health, then charge another while standing in front of him. He should hit you and bounce off, stopping the attack. Lock on as he flies back up, releasing your shot as soon as you see the blue "aura" around his body; that's the moment he becomes vulnerable.
Helios will return to ground level and your phazon meter will be low, but you can recharge it now that you're corrupted. Charge a shot and wait for him to come down, releasing it when he does. Hold up and run into him to repeatedly get hit. This will help you stay in hyper mode if you would have lost it from that charged shot, as well as give the phazon you'll need to finish him without a second hyper mode.
When your meter's about half full, back off and try to get him to bounce off you again when he does the slashing attack. It's not easy to do this since you were just in his face, but you can't afford to let him waste time. As before, release a charged shot when you see the blue aura, then quickly release a medium one to finish him before you auto vent. There isn't enough time to charge it up to full, and a slight charge is not enough to kill him.