Every character in any anime is made accordingly for playing his/her role supporting the protagonist.Some are strong and some are weak but every character plays his/her role efficiently. Below here we have listed some of the strongest side character.Even you can mention the name of character you think is strongest.
Toshiro Hitsugaya -Bleach
Hitsugaya is a captain of the Gotei 13, a group of Soul Reapers who govern the flow of souls and protect Soul Society, an afterlife realm. Hitsugaya makes appearances in all Bleach’s films, being the protagonist in The Diamond Dust Rebellion Hitsugaya’s character has been well received among both readers and reviewers, becoming the series breakout character. Amongst the Bleach reader base, he has been highly popular, placing high in several popularity polls too
Near -Death Note
He was as smart as L the world famous detective.(SPOILER)After death of L Near was the character who caught Light Yagami.