Answer: won
Explanation:
The correct sentence would be:
The lawyer had won the case. We should note that had is typically utilized as an auxillary verb which is then used to make the past perfect.
We should note that the past perfect of win is won. We can't use "win"wins or "wins" because it's not an ongoing action or an action that hasn't been carried out. Also using winner is grammatically incorrect.
Therefore, the best option is won.
