Swampfire

He may look like a walking compost heap, but he is one of Ben's strongest aliens.
Swampfire is a Methanosian from the planet Methanos. Swampfire is a plant-like alien with a flame-patterned head. His powers are a combination of those of Wildvine (having his body made of plantmatter and being able to command them,) Heatblast (the ability to shoot fire) and Benmummy (regeneration), who are from the original series. He has super strength, vast regenerative powers, the ability to control plant life through a type of gas, and the ability to emit fire from his palms. His regenerative ability also allows him to alter his own body, such as tunneling underground in vine form or growing his feet to root himself into the ground. Swampfire is Ben's first transformation when the Omnitrix is recalibrated in "Ben 10 Returns".