My Hero Academia vs One Piece

Connection:

Both are villains hailing from iconic Shonen series who started out as orphans before being taken in by extremely powerful leader figures from opposite sides of morality (All For One and Whitebeard respectively) and joined their cause. As time goes on though they became leaders themselves of a villainous organization (League of Villains and Blackbeard Pirates respectively)

Both changed their names upon becoming villains and accepting their powers (Tenko Shimura was "reborn" as Tomura Shigaraki, the latter's name coming from All For One and Marshal D. Teach changing his name to Blackbeard after devouring a Logia Devil-Fruit he stole after killing Thatch)

Both also gained an even higher status (Shigaraki became the leader of the Paranormal Liberation Front and Blackbeard is one of the Four Emperors)

Both have an ability that allows them to destroy almost anything they touch (The Dark-Dark Fruit/ Yami Yami no Mi and Decay Quirk respectively) 

Both seek world domination with important tools (All For One Quirk and The One Piece respectively

Both would ultimately betray their former masters with the intent on becoming more independent and inherited new abilities they got from them (All For One Quirk and the Tremor-Tremor Fruit/ Gura Gura no Mi respectively). Both also gained the ability to steal powers (The Dark-Dark Fruit/ Yami Yami no Mi and All For One Quirk respectively)

Both also act as the evil counterpart and dark reflections to their series' main protagonists (Izuku Midoriya and Monkey D. Luffy respectively)