"I can think of no greater punishment than answering your question in full."
—Lazav

Thought Collapse

Counter target spell. Its controller mills three cards.

Jumpstart

The List

Ravnica Allegiance

Counter target spell. Its controller puts the top three cards of their library into their graveyard.

A spell that can’t be countered is a legal target for Thought Collapse. The spell won’t be countered when Thought Collapse resolves, but its controller will still put the top three cards of their library into their graveyard.