if i understand class correctly, he hasnt won recently for a long time and when he revenges the other player from the revenge tab and looses it, then it shouldn't generate another opportunity to get revenged again. it sounds a lot to me like that player who is killing him several times a day is exploiting something and should be looked deeper into before this becomes a server wide habit. on my server i am the highest ranked player on level and i can only revenge when someone attacks me at sea. if i win the revenge i dont get another for the rest of the day and the next day i only get a revenge when the opponent managed to actually win one. i have however 10+ players sending me revenges daily (i assume its for the quest) which is fine for me and it will not generate a revenge for me either. so i look daily at the big screen telling me there is no open revenges for me.
the only thing i can think of in this case is that the other player could maybe be 3+ levels lower then you are and that is why you woudnt get a revenge on him... but you did say you have open revenge against him so i really dont know what you did or what he does to be able to trigger multiple revenges during the day even while you dont attack him.