its impossible to turn a Pokemon imunne to everything, the same for resistant t everything
grass has too many weakness, so theres no type combination that would work except from fairy/steel with flash fire skill-swapped and this one isn't imunne to everything. but it has no weakness. trick-or-treat will not work as only Normal & Dark resists Ghost. Dark/Ghost will have Fairy Weakness and Normal/ Ghost will still have Dark weakness. soak won't work as it basically just turns the target into a water type, so no: no type combinations will be imunne to everything with trick-or-treat or forest curse
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