Which two characters of Lord of the Flies can be best compared?

I would go with Ralph and Jack. They are almost opposites. They represent two parts of society. Ralph is the responsible democratic leader and Jack is the autocratic socio-path. These two actually feed on each other. It is a game of control and minipulation until Jack simply appeals to the primal desires of the boys. At this point he takes over. If you need more help just let me know on this thread.

Simon and Roger would also be a good choice. Simon is gentle and well liked by the little 'uns. Roger is a viscous bully who feeds on the fear from the same group that adores Simon. I would agree with the above answer though as the easiest route. From personalities to physical descriptions, they are definitely opposites.