I dont think Darkness can kill just about anybody with Darkness in their heart, ive never seen him do that but he can attack via shadow and crippled you from the inside..
In the Hulk/Darkness non canon crossover his menions couldnt eat the Hulk but that was an attack coming from outside, how about attacking from inside say taking out the brain and heart, i dont think the hulk can heal from that, he could also calm Hulk down bringing banner out..