Curse of Inertia

The ability won’t trigger when a creature attacks a planeswalker controlled by the enchanted player.

Even though the attacking player chooses the target of the ability, the ability is still controlled by the player who controls Curse of Inertia. Notably, a creature with hexproof controlled by the player who controls Curse of Inertia could be chosen, even though another player may be choosing the target.

A Curse spell targets the player it will enchant like any other Aura spell, and a Curse stays on the battlefield like any other Aura. If the enchanted player gains protection from the Curse’s color (or any other characteristic the Curse has), the Curse will be put into its owner’s graveyard.