Deadpool started out as Ruber's partner and both he and Ruber were hated for being self-centered, uncaring for the people, and for Deadpool, his rude-word play.
when he requested to have Dark Cynder become queen of camelot, Lionel stated, "I will not serve that horrible witch!' Deadpool reacted with a question, "Wanna see if you have an unbreakable skull?" then killed him, which started a fight.
But both he and Ruber were scared off by Arthur's might and Excalibur.
Later, both he and Ruber joined the Villain League and tried to gain control over Camelot, but they were bested and defeated by the Shell Louge Squad.
Deadpool was later seen at the end, rejoicing his victory of still being alive before getting stepped on by the giant rock orge.
Since he can't die, he appeared again in SpongeBob and Friends Find The Black Cauldron, but after the Horned king's defeat, he and the other villains retreated due to the Black Cauldron sucking the castle to the banished realms. He then appeared in the side story in SpongeBob and Friends Meet Lilo & Stitch where he is helping Jafar, Maleficent, Fagin, Ratigan, and the Heartless to capture Princess Jasmine. Sadly, it was successful.
He is assumingly bound to return to get revenge but it is unsure it he will have his dark humor controlled by then.......... assumingly not. He will get revenge on the Shell Louge Squad in Spongebob & Friends Meet Oliver and Company with Savio.