I think it's B>A>C>D as B is the most threatening and likely to function as a trade. A still has utility with trying to trade though, and has on-kill effect synergy. The threat of C is in my opinion totally ignorable if you use it on enemies, and you really should be swapping with magic-immune stuff, but the problem is you need to get both the immune thing and this unit into position to get a good attack off at all. D is a joke, compel is already arguably not a negative effect.