Boss Returns 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

After being backstabbed by one of his own men, the boss of a nationwide gang, 'Baek GangHoon,' finds himself regressed to his high school days! Can he start a new life without violence to prevent a repeat of his wife's death?