You fight Death to the death so you can live forever
The old saying that no one can avoid Death or Taxes is half-true in your case: you haven't paid taxes in your life, all because the tax man is too afraid to collect from a fighter like you. Now it is time to deal with the second half of that equation to become the greatest fighting man that ever there was.
Now it is time to fight DEATH.
Thanks to the marvels of the internet, accessed quickly and freely at your local public library, you are quickly able to pull up instructions on how to summon Thanatos, the personification of Death itself. The ritual instructions say that the meeting must take place at night after a week of preparations, a week during which you cannot sleep, and that is perfectly fine by you, as you never sleep since defeating the Hypnos in an arm-wrestling match. There are to be long salty baths, exotic meats, and even more exotic cheeses, all to be prepared by special servants you bless with magic dust and holy communion wine. None of this makes much sense to you, but, for the chance you've been waiting for, you'll do anything.
After conscripting your servants with threats of punching, and procuring the necessary salts, meats, cheeses, dusts, and wines (with more threats), you set to the task of ritualizing. For hours each day you soak in salt water baths, and for hours you eat and eat, consuming enough protein to make for a horror show every time you manage a bowel movement. At the end of the sixth day, you feel like dying, but that is not the same as summoning Death. It is only on the seventh day, at the last stroke of midnight, that the vortex opens and you get your chance...
Alas, all that effort, and it turns out Death is a really awful fighter. You pop his greasy skull off with one upper cut, then pull off his skeletal arms and beat him to pieces with them. Triumph as you stamp the skull to bits, grinding bones into powder under your heavy boots, laughing and laughing. You've won! You've proven to everyone that you are the best!
Or... so you thought. You have defeated Death, true, but, as it turns out, fear of Death was the only reason you won so many fights with living souls. As no one fears Death any longer, you are constantly getting your ass beat down... forever.
The End.