Note: Jeff is stronger via calc, but ST is arguably more mobile via either teleportation/flight. ST however can't spam teleport, and it isn't even in character to use the ability in combat at least not right away.
Skin Taker would likely win due to his type 7 immortality, while yes Jeff scales high stat wise the difference shuldn't be so big where Skin Taker can't hurt him decently so he'll be able to shrug off more damage
Cause it does on skeletons and undead in other media and he never shows those stats. If you think ST should have Type 2 or Pain resistance feel free to make a thread. Would support the changes, but as it is right now ST doesn't have that. Also do note Jeff is a better fighter and his first move will be to incap ST, so it isn't like ST will be able to get many hits in. Plus Jeff is far more intelligent. ST could potentially get away with teleportation or flight, but his teleportation isn't the best and if he flies away he will eventually have to come down to attack Jeff. Even with damage resistance, it is hard to inflict damage when you are pinned against the ground.