The terms virtuous circle and vicious circle are defined as complex chains of events which reinforce themselves through a feedback loop. A virtuous circle has favorable results, while a vicious circle has detrimental results.

"Vicious" doesn't have a comparative and superlative form. Instead, you would say "more vicious" or "most vicious."

There is no noun for the word "vicious". "Vicious" is an adjective.

Vicious the Echidna is the more powerful incarnation of Vicious the Hedgehog