Leonardo (TMNT Live Action 2014)

Leonardo is the main characters of live action movie, Teenage Mutant Ninja Turtles. He is the brother of Donatello, Raphael, Michelangelo and adoptive son of Splinter.

He is portrayed by Pete Ploszek portrayed Garrett Douglas from Teen Wolf in motion capture and voiced by Johnny Knoxville.

Personality
He is dedicated to perfecting his ninjutsu skills and will stop at nothing to defend his brothers and the entire city. There are times where his cautious nature makes him clash with his brothers. Leonardo firmly believes it's his ninja duty to protect all people. He tends to have a similar personality to his '87 counterpart where he is determined to help people and keep his brothers in line. He and Raphael unlike in their other adaptions don't fight over leadership although they have a brief argument over the Hamatshi and Raphael talking about leaving which Leo debunks Raph's claim. In the movie he, like Donnie and Raph, doesn't seek April's attention unlike Mikey who does.

Teenage Mutant Ninja Turtles
April, at the scene, becomes a hostage herself. Four mysterious figures arrive, take out the Clan, and free the hostages. April follows them to a rooftop and is shocked to see that the vigilantes are anthropomorphic mutant turtles, causing her to pass out. When she regains consciousness, they advise her not to tell anyone of them. As they leave, April hears Raphael and Leonardo's names.

April returns to her apartment and remembers "Project Renaissance", her father's science experiment, which involved four turtles named Leonardo, Donatello, Michelangelo, Raphael, and a mutated rat called Splinter. Unable to convince Bernadette of the Turtles' existence, April is dismissed.

At Splinter's behest, the Turtles bring April to their sewer lair. Splinter explains April had saved them all from the fire and freed them into the sewers. The mutagen caused the five of them to grow and develop humanoid attributes.

Shredder and the Foot Soldiers attack the lair, defeating Splinter and incapacitating Raphael while the other Turtles are captured. April comes out of hiding and she and Raphael plan to save the others. At Sacks' estate, he has the Turtles' blood drained in order to create an antidote to a deadly virus that Sacks hopes to flood New York with, believing he will become rich from people seeking his cure. Raphael, April, and Vern storm the estate and free the other Turtles. The group then escapes the compound in pursuit of Sacks.

April and Vern subdue Sacks in the lab, while the Turtles are battling Shredder on the roof. During the fight, the tower's support beams collapse. As the turtles try to keep it from falling and infecting the city, April confronts Shredder with the mutagen. In the struggle, the tower collapses and the Turtles pull April onto it with them, while Shredder falls to the street and is captured by the police. Believing they are about to die, the Turtles confess their secrets, while Raphael gives an impassioned speech of his love for his brothers before they land harmlessly on the street. They vanish before the humans find them and return to the sewers, where they give Splinter the mutagen and he begins to recover.

Sometime later, Turtles appear in a special modified "Turtle Van", and Michelangelo accidentally blows up Vern's new car with a rocket. As police respond to the explosion, the Turtles leave, but not before Mikey tries to serenade April with "Happy Together" by the band The Turtles, much to his brothers' annoyance and April's amusement.

Teenage Mutant Ninja Turtles: Out of the Shadows
Two years after their battle with Shredder and Eric Sacks, the Teenage Mutant Ninja Turtles, Leonardo, Donatello, Raphael, and Michelangelo, still live beneath the sewers of New York City, having allowed Vern Fenwick to take the credit for Shredder's defeat. At Grand Central Station, April O'Neil discovers and informs the turtles that scientist Baxter Stockman is working for Shredder and plans to bust him out of prison.

Trivia

 * In Teenage Mutant Ninja Turtles: Out of the Shadows, Knoxville didn't return to voice him, and Ploszek provided both motion-capture and voice.