Sekiro's Man Without Equal achievement requires you to kill a lot of bosses. In fact, it requires you to kill all of them, but that's not quite as easy as it sounds (and it already sounds pretty daunting if you're having trouble beating the game's first mid-boss.
To even reach all of the bosses required to get the Man Without Equal achievement, you'll need at least two separate playthroughs on the same save file. In addition (and without spoiling too much) one of these playthroughs will have to be a "Shura" ending to unlock a final boss fight (if you need to know how to unlock the Shura ending, check here). And then, just to make matters a little complicated, there are some late-game bosses that can't actually be fought when you are pursuing a "Shura" ending. If that sounds a little confusing, let us lay out all of the bosses you'll need to beat to get the Man Without Equal achievement.
Which bosses to beat to get the Man Without Equal achievement in Sekiro
This list is in roughly the order you'll encounter them in your playthrough. If there are any that are optional or MISSABLE then we'll provide a short description of where to find them, and then if there are any that you must complete on a NON-SHURA playthrough we'll also let you know so you can make sure to get them on your first go round.
Gyoubu Oniwa – The horse lad, you can't miss him.
Lady Butterfly – MISSABLE She's in the Hirata Estate memory, proceed through the estate to the end to fight her.
Genichiro Ashina – The guy who cut your arm off at the start. You'll encounter him again on the roof of the castle, if you need help with how to beat Genichiro Ashina then allow us to be of service.
Guardian Ape – Again, you can't miss him, very large monkey in your way. If you need help with how to beat Guardian Ape then we've got you covered there, too.
Folding Screen Monkeys – Also unmissable, though smaller than the big one above. If you need help with how to beat the Folding Screen Monkeys then check it out.
Corrupted Monk – Further on in the story, but still impossible to miss as you progress.
Headless Ape – MISSABLE You'll find this lad in the Ashina Depths just after the poison pool. The tricky part is that you'll need to beat Guardian Ape first, but although he's technically undying you won't need to find the Mortal Blade before you take him on.
Great Shinobi - Owl – NON-SHURA although since this is a mandatory boss you'll beat him on your longer playthrough before going back and choosing the Shura ending path. Or you can do that the other way round if you want. Just make sure you get him done.
Corrupted Monk - True Monk – NON-SHURA Another mandatory boss for your longer playthrough, so don't worry about it.
Divine Dragon – NON-SHURA Again, mandatory for your longer playthrough.
Demon of Hatred – MISSABLE and NON-SHURA This angry lad's in the Ashina Outskirts by the first gate pathway idol but only after The Sculptor leaves when the castle is on fire. Due to him being missable and not being able to pick him up in a Shura ending playthrough, this is one that you absolutely have to pick up in your longer playthrough if you're being efficient.
Sword Saint Isshin – NON-SHURA but mandatory, don't fret.
Owl (Father) – MISSABLE Only appears as a mandatory boss in Purification ending runs, however you can find him during Immortal Severance and Return endings, but you still need to meet the requirements for a Purification ending. If you need to know how to get the Purification or Immortal Severance ending for Sekiro, check this guide out.
Emma, the Gentle Blade + Isshin Ashina – This is your secret boss for the Shura ending playthrough. You can't miss 'em.
And that's it! Congratulations! Now that you know how to get the Man Without Equal achievement in Sekiro, you truly are the greatest shinobi of all. But at what cost? At what cost...