Splinter

Background
Splinter or Hamato Yoshi is the father and formal leader of the Teenage Mutant Ninja Turtles. He is a Grand Master of Ninjutsu training his son's in the art of Ninjutsu. As well as guiding them through the hardships they'll encounter on the surface world. Splinter also is very protective of his sons, and also can be hostile at times. However, his love is always evident. Splinter is one of the few who could survive a battle with Shredder. It's also evident that Splinter could beat Shredder in a one on one battle through flashbacks. However, this cost the life of his wife and baby daughter. After this he moved to New York to hide from his enemy, and this would eventually change his life forever.

Training
Splinter is possibly trained in all 18 disciplines of Ninjutsu which he learned and refined over the years. He was trained by the Ancient One a member of the Ninja Tribunal. This makes Splinter a formitable opponent and skilled fighter. He also seems to have refined his mind over the years as well.

Battle with Shredder
While the battle between Shredder and Splinter are seen through flashbacks it's known that Splinter was able to beat Shredder slightly. But, only at the lose of his wife and daughter during the fire that Shredder caused during the fight. Splinter explained that hatred brewed over the love of a women, and this fueled the rage inside Shredder causing him to take his hate out on Splinter and his family. Shredder has never shown remorse for his actions, and is in fact on a vendette to kill Splinter and the Turtles.