Conversation so far:
What was Leonardo of Teenage Mutant Ninja Turtles like in the original trilogy?
In 1990 film Teenage Mutant Ninja Turtles, Leonardo was fairly modest and sensitive, rarely issuing direct commands.
Did Leonardo of Teenage Mutant Ninja Turtles have any specific fights with villains in the original trilogy?
Leonardo of Teenage Mutant Ninja Turtles fought alongside his brothers against The Shredder in the climatic battle.
Did Leonardo of Teenage Mutant Ninja Turtles defeat The Shredder?
Leonardo of Teenage Mutant Ninja Turtles was the only one of the four to actually injure The Shredder, but, like his brothers, could not defeat him.
What weapons does Leonardo of Teenage Mutant Ninja Turtles use?
Leonardo of Teenage Mutant Ninja Turtles' signature weapons are two Ninjatos, commonly confused as Katanas.

Question: Why did he and his brothers fight The Shredder?
Self-contained rewrite: Why did Leonardo of Teenage Mutant Ninja Turtles and his brothers fight The Shredder in the 1990 film Teenage Mutant Ninja Turtles?