Despite the comedic nature of the Ernest film series, Felix was actually a rather fearsome adversary, though like most comedy villains, he was defeated by Ernest and made to pay for his many crimes.
Felix was a convicted crime lord on death row who also happened to look identical to Ernest; this would allow him to come up with a plan to switch places with Ernest and evade death row while having Ernest falsely imprisoned so as to fool the guards into thinking Felix was still in prison.
As Ernest tried to reform the prisoners in his own eccentric (but well-meaning) way, Felix proceeded to try and ruin Ernest's life, but was angered at the way people dismissed him and thought he was doing Ernest a favor when he started to commit mean-spirited acts and criminal behavior that alienated him from Ernest's friends.
Ultimately, Felix masterminded a plan to rob Ernest's own employers, who just so happened to be a rather prominent bank. Felix's death row inmate Lyle grew attached to Ernest and felt guilt over letting an innocent man die just so Felix could further his own criminal lifestyle, which ultimately resulted in Ernest escaping prison. Rubin tries to stop Ernest from escaping the prison at its main gate, but Lyle tells him to spare Ernest. After knocking out Rubin, Lyle releases Ernest, who tells him goodbye afterwards. Ernest engages Felix in a battle after arriving at the bank.