How do you deal with someone who is vastly stronger than you?
Training! It's a tried and true tradition of heroes that they train themselves, honing their bodies and minds into steel, or some other suitably hard metal, before fighting an evil overlord. I mean, after all, to even get to the guy, you're going to have to cut through endless hordes of weaker enemies! And that requires endurance, will, and, preferably, a plentiful supply of water and nutritious snacks! Heroing is hungry work!
It goes without saying that being a hero requires a certain level of physical fitness, but no matter how strong you are, there is always someone out there who is stronger than you. This is why a hero must always fight smart! Use the GOLD system!
G - Get Allies. Find as many as you can to help you in your fight. Even if they are not strong individually, each one is a distraction your enemy has to deal with and waste energy on.
O - Order equipment. Be sure that everyone who is coming to the fight has what they need to fight. Swords, shields, armor, whatever. You don't want to watch your allies getting mowed down because they don't have any way to defend themselves.
L - Learn their weaknesses. Figure out any special weaknesses your foe my possess. If you are fighting werewolves, bring silver. If you are fighting vampires, bring wooden stakes. If you are fighting politicians, bring honest facts. Use those weaknesses when you plan your attack!
And most importantly...
D - Don't die! Even if you have an army with you, the best equipment, and a perfect plan for all of your enemy's weaknesses, sometimes that just isn't enough. When that happens, have an escape plan. Live to fight again tomorrow. The dirt is filled with the bones of dead heroes and none of them are of any use to anyone! So if you are in a situation that is completely hopeless, retreat is a perfectly valid option. Don't let any honorbound musclehead tell you otherwise!
Stick to the GOLD system and sooner or later, all of your foes will fall before you and, most importantly, you will survive to reap the rewards!
Thanks for your question!