Ocean Liners are not the first thing to come to mind, when you think of sinking warships. And, yet, it has happened more than once. Albeit mostly by accident, but there is at least one case of an intentional ramming by an ocean liner.

That example, and two accidents, are featured in this video. Ranging from a crippled destroyer, to a cruiser cut in two.

Further Reading:
https://navyhistory.au/ss-queen-mary-...
https://www.history.navy.mil/research...
https://www.amazon.com/German-Submari...
https://www.amazon.com/Olympic-Class-...