Flamethrower is an old villain. He is a shanklor who disguises as a man.
He is first seen as a carnival man in a tent. When Ventro comes to stop him once he hears all old villains are coming back to start a plot to defeat Ventro, Flamethrower tries to bribe him into thinking he's innocent. Ventro doesn't belive him, so Flamethrower has no choice, but he has to turn into his true form. A monster. Ventro stops him. Later on, he bets Ventro Jr that he can't get the new chargeball stadium for $30. In the last episode, Jenny goes crazy and almost kills Flamethrower. At the end of the episode when Ventro blows up the bad guy stadium, it is unknown what happened to Flamethrower. He probably survived the events, but went into hiding.
Flamethrower is seen getting the invitation for the "Villains of Tomorrow" comittee and goes. He is one of the ones who captured Ventro. Ventro escapes and arrests Flamethrower.
It is unknown where he is now. He is probably rather in jail or hiding.