Soak: 2x damage, since the Pokemon changes into a pure water type, making it only weak to Grass, Electric, and Freeze Dry. One-type Pokemon cannot take 4x damage from anything.
Forest's Curse: At least 2x damage, depending on what the Pokemon's type is. For example, if a Pokemon 2x weak to Ice/Freeze Dry gets Forest Cursed, Freeze Dry would do 4x damage due to its typing. For example:
Bibarel + Forest's Curse = Normal + Water + Grass |
^2x Weak^ | 2x * 2x = 4x Weak
Now, if a Pokemon 4x weak to Freeze Dry gets Forest Cursed, Freeze Dry would do 8x damage. Example:
Kingdra + Forest's Curse = Dragon + Water + Grass |
2x Weak: ^ ^ ^ | 2x * 2x * 2x = 8x Weak
Source: Knowledge of Freeze Dry