Mouhitori no Saikyou no Ore -Teihen Kara no Nariagari- is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Tokiwa Ren, a poor and timid boy, was living at the bottom of the school caste system in a prestigious private academy. However, one day, the personality of the “strongest delinquent” who was sentenced to death takes residence within Ren, completely overwhelming his bullies! With “his unimpressive self” and the “undefeated strongest personality” now at his disposal, Ren decides to overturn the school’s power structure by confronting the “upper-class citizens” who rule the school, including the sons of politicians and heirs to major corporations! As the timid boy is manipulated by the delinquent’s personality, he climbs to the top of the school hierarchy. A school battle drama of reversal where “justice” and “evil” collide begins here!!! Original Webtoon