Dungeons 3

This is done in the "Twistram in Ruins" level. To collect Evilness in Dungeons 3, you need to find the Islands of Good guarded by Heroes and defeat them. They are not Islands in the traditional sense, just areas in the map. Once defeated the Island of Good corrupts into a Island of Evil which will continually give out Evilness. There is no need to collect it as the game will automatically collect Evilness once the Island has been corrupted. You can find these Islands via the in-game Overworld mini-map on the bottom left.

Collect 1,000 Evilness for the trophy but you don't have to hold 1,000 at a time for the trophy, it will pop the moment you've collected 1,000 Evilness over time. You'll get used to this since Evilness is an essential resource in Dungeons 3. If you're spending Evilness just keep playing until the trophy pops.