I play Sabotage and my opponent responds with a Thrill of the Hunt, move a unit to an battlefield. What resolves first?

The Thrill of the Hunt resolves first.

Sequence of Events:

1. Sabotage is played as an [Action] (Open State). It is placed on the chain as a pending item.
2. Thrill of the Hunt is played as a [Reaction] by your opponent in response. Because it is a [Reaction], it is placed on top of the existing chain.
3. Chain Resolution (LIFO): The chain resolves in reverse order (Last-In, First-Out).
   • Thrill of the Hunt resolves first.
   • Sabotage resolves second.

According to Rule 340.1 and the standard LIFO (Last-In, First-Out) resolution of the chain, the newest item added to the chain is always the first to resolve. RiftJudge FAQ #5035 confirms this behavior: "The chain resolves from last to first, meaning the last effect added to the chain resolves first."