AC includes your charisma bonus.

melee attack with
1d8 + slash damage charisma modifier

can attack with both strength and dexterity

Your Intelligence score increases by 1, and your Charisma score increases by 2.

devils can live forever unless they are killed in hell

Tieflings might not have an innate tendency toward evil, but many of them end up there. Evil or not, an independent nature inclines many tieflings toward a chaotic alignment.

Your base walking speed is 30 feet.

Thanks to your infernal heritage, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You have resistance to fire damage.

The corrupter can use his action to
morph into a Small or Medium humanoid, or back
to its true form. Without wings, the corrupter loses his
flight displacement. Also, its size and
displacement, your stats are the same in each shape.
Any equipment he is wearing or carrying is not
is transformed. It reverts to its true form if it dies.

You can speak, read, and write Common and Infernal.