TMNT: Earth-19/Leonardo

Early Life
Originally, Leonardo was a regular turtle growing up in a scientist's lab alongside three other turtles and a rat. Eventually, during a mass break-in, the five were knocked outside and were covered in strange green ooze.

The ooze caused them all to start developing incredible intelligence, with Leonardo being the most developed out of all of them due to being exposed to the most ooze.

One of their members was attacked by an alleycat but was saved by the rat, who had taken the name "Splinter". However, after this attack, the turtle became incredibly hostile towards his brothers.

Splinter, after discovering a book about old renaissance artists, decided to name his adoptive sons, finally giving Leonardo his name and dubbing his brothers Raphael, Donatello, and Michelangelo. Splinter also gave all of his sons red masks to symbolize the red belt.

Splinter claimed that they would receive different colored masks when they proved they had learned discipline, which sparked a large argument between Raphael and Leonardo when Leo was the first to gain a different colored mask.

This argument ended in Raphael leaving, with Leonardo waking up his other brothers and, despite the orders of Splinter to not go outside, went on to the surface to look for Raph and bring him home.

Powers

 * Mutant Turtle Physiology: Leonardo is a giant mutant turtle and thus has the abilities of his non-mutated brethren.
 * Amphibious Nature: Leonardo is able to survive on land and water and can switch between the two easily, though he still needs to breathe and staying underwater for too long could drown him.
 * Turtle Shell: Leonardo shares the shell on his back with the rest of his brothers. It is fairly strong, able to withstand direct blows from swords and more.
 * Enhanced Intelligence: While quite the obvious fact, Leo is much smarter than the average turtle.

Abilities

 * Hand-to-Hand Combat (advanced): Leo is the most gifted of his brothers when it comes to martial arts and has learned several styles from all around the world.
 * Ninjutsu: Leo has been trained by both Master Splinter and the Foot Clan and thus is quite adept when it comes to the art of ninjitsu.
 * Stealth: Leo's motto is "strike fast then fade into the shadows".
 * Disguise: Using very heavy clothing and surgical masks, Leo is able to disguise himself and walk outside, though this only works at night when people can't see him properly.
 * Kenjutsu: Throughout his life, Leo has been drawn more to the sword as a weapon than any others. Due to this, he has become a master of kenjutsu fighting techniques.
 * Kyujutsu: While preferring the sword as a weapon, Leo is an incredible archer and will use a bow if it is clear that his close-ranged fighting style won't cut it for him.
 * Master Acrobat: Leo is an incredible acrobat, able to bend his body in ways that would strain a normal person heavily.
 * Leadership: Leo is the de-facto leader of his brothers and is very good at it. In situations where he works with people other than his brothers, Leo usually becomes the leader of the temporary group as well.
 * Master Strategist and Tactician: During battles, Leo's mind is his greatest asset as he is able to think up battle plans on the spot.

Paraphernalia

 * Twin Katanas: Leonardo's most used and favorite weapons. A pair of katanas that were forged by the late father of Hamato Yoshi. The katanas are Leo's prized possession and he does everything he can to keep them out of harm's way.

Notes and Trivia

 * In spite of his usually level-headed and calm attitude, Leo is known to have an egotistical streak. He is aware that he is the most capable of his brothers and thus has trusting them to "do it right".
 * Leonardo is incredibly close to Splinter and all of his brothers believe him to be Splinter's favorite. Due to this, Raphael has dubbed him "Splinter's Pet".
 * On a more light-hearted note, Leo is easily embarrassed and will do an awkward-sounding scream when caught off-guard. He also will try and save-face by instantly going back to being serious whenever he becomes "too happy".
 * Leo's room in the Turtle Lair is modeled after a Japanese dojo. It has a meditation rug in the middle of it, a sword collection on the wall, a sleeping bag, a table, and nothing else.