Seeing that one of the wolves against him was the source of strength to the other one, Logan decided to lure the other wolf into attacking him. Using his abilities, which he gained through years of training and discipline, he brought the wolf who attacked him down.
None of the wolves against Logan was stronger but being together made them strong against him, thus, he had to be smart. It wasn't just about how strong and powerful he was but also how he applied and made use of his power.
Immediately, the wolf who depended on the other wolf attacked him, Logan sped up and shut him down, making him weak and useless for the time being.
This gave him the opportunity to attack the strength giver. It wasn't a hassle for him because all the strength giver wolf could do was donate strength and power but didn't possess much ability to defend himself and fight so killing him was easy.
