Building when fed

So basically I have two friends that like to play support, so one goes "support" top and I have to gank alot, the other support bottom. Often it results with us all being fed because we have a constant barrage of healing/shields/ex, one of them plays Kayle whose R makes you "immortal" for a few seconds, so I was thinking, what do I build when I'm fed? I would like to build full AP warwick and basically one shot everyone with immortality. Sounds kind of noob but they don't really play ranked so yeah, what do you suggest I build?