[Pearls are the worst. Would it be wrong of her to go find that pillar she stuck the happy pearl in and try hugging it to see if it helps?]
I already tried killing him. Didn't work out. Also, wouldn't have mattered apparently. [What with Ianto coming back Tyki would have just come back too...probably.] So, I'll have an answer to that question you aren't asking as soon as I figure out what's more permanent than death.