How can I quickly defeat someone who has no armies or holdings?

Recently I had someone with zero troops, no holdings and no vassals declare war on me, attempting to press their claim of a single county of mine. The only title they have is a duchy level titular title.

Now it is clear to me that they cannot win this war, ticking war-score will eventually bring me to 100. However this will take a very long time and I would like to not be at war at some point so I can make raiding parties.

I thought that I might be able to assassinate them to end the war. However you may notice that they only have one other person in their court. That person refused to join my plot and then died anyway, leaving no-one to join my plot. I believe that regardless of plot power I do need someone else in my plot for it to be successful, so it seems impossible to murder them.

Is there any way I can end the war other than ticking in this scenario?

If it matters the Tengrikut is currently residing in my realm.

A good option here is to just offer white peace. Your opponent accept it far earlier and it only gains you 50 prestige less than winning the war would. If you intend to raid with your peace time then you will surely make up the 50 prestige with the raids you are able to do.

However if you give them white peace they will retain their causum belli, meaning they might, in the future attack you again with no armies and holdings.

I don't believe there's anything you can do. I find it most often happens with religious heads. In my most recent game as Scandinavia, I had it happen every ~30 years with the Catholic pope launching a crusade on me. And then I would have to click through ~200 messages stating each and every Germanic ruler pledged to defend me.

Honestly, I wouldn't consider it cheating to pull up the command console and just force-end the war. Take a white peace so you don't get any unfair rewards.

CK2 just isn't really designed for huge campaigns. It's too easy to force annoying edge cases like this.