Cristo is a member of the Purple Dragons, first appearing in the very first comic. Here, he was unnamed, just appearing as a mustachioed member of the gang in a vest, holding a gun.
He reappears much later in Tales of the TMNT vol. 2, #57, where he is named and fleshed out slightly. Here, he is shaken down by Chucky and the Madhattan Maulitia, who they are in opposition to Cristo and the Dragons muscling in on their territory. His apartment happens to be right across from April and Casey's, and a gunshot during their squabble send the turtles scrambling over to stop them. After the turtles dispatch the Maulitia, however, Cristo shows no favor to his saviors and pulls a gun on them, wanting revenge for beating him all those years ago. Cristo, to his misfortune, is easily taken out again.