Mazinkaiser SKL, Garo: Vanishing Line Recommendations
While there is no Mecha in Garo: Vanishing Line, they do share some similarities. In these two anime, you have a violent badass main character that fights against evil powerful beings. They have a similar manly tone to them as they both have heavy metal music, plenty of nice action scenes and lots of violence/blood. You can get testosterone fueled rampage of enjoyment in both of these two anime.