The American opossum is a close runner up for objectively cutest marsupial, however they do have more teef than any other North American land mammal, making them a little more scary
The thylacine, or Tasmanian tiger, is a really cool looking carnivorous marsupial. The last living Tasmanian tiger was captured in 1933 and the species is now extinct. Beautiful, but pretty scary.
Koalas are lowkey terrifying- a quick internet search says they regularly eat poison and can be more aggressive than a crocodile. Just look at those claws. Don't invite him in. Scariest beasty on the list by a long shot.