"We need to kill him so that he can't stand in our way". I really can't understand this logic. It is established that he is crazy strong, maybe as strong as their guildmaster, they know that he as a grudge against their guild and their plan is to attack him again ? It's the BEST way to have him stand in their way, he already have a grudge against their guild, if they keep attacking him he's just going to come kick their ass so that they stop bothering him.
Instead, they should try, first, to know why he has a grudge against the guild, trying to fix that, and then trying to get a friendly relation. Even if they don't recruit him.
Whatever, go get your ass whooped it's going to be entertaining