MC is trained by the 2 strongest in the world to the point no one short of the hero who beat them would be able to beat him, loses to rando so that he can have a bullshit shōnen ass pull power up. These last 2 chapters have really lost me because he didn't get beat because of his personality...
Reminds me of Ruby Weapon. I was in a blind panic the first time I fought it and the party was drained when its HP hit 0 only for the bosses HP bar to fill back up. We managed to win and it was certainly a thrill.