Rakudai Kishi no Cavalry, Saijaku Muhai no Bahamut Recommendations
Just to add some more info
Both MCs are really strong warriors with an unfortunate past. They both have a messed up family. They both are also really kind to the point where they can be naive.
Both Female leads are Tsundere Princesses who meets the MC in an embarrassing way and challenges them to a fight only to like them a lot after it.
(Ep 1 only)
Both MCs Have a little Sister with a Bro complex
Both series have a battle school like setting
Both have a main character that seems weak but in the final is Super OP.
They too have girls that love the main character when discover he is op.
Both mains are in a school that hate they (in Saijaku theres only a man in the school thats the main character and he in the begginer everyone hate him/in Rakudai the girl start to hate him and his family hate him too)
- Very powerful male characters, both having titles of the so called "weakest undefeated"
- Similar harem and ecchi themes
- School-centered duels
Both MC's share similar characteristics with being viewed as weak, yet unknowingly heavily OP. Both [MC's] also deal with tragic pasts revolving around their families