Dennis Reynolds is selfish, vain, nasty, and obsessed with himself. As a result, he often acts as a bad influence on the Gang and makes them worse. From his uncontrollable rage to his serial killer-esque qualities, Dennis doesn't help his friends become better people.
On multiple occasions, Dennis has said that he is the Golden God. His entitlement runs rampant throughout It's Always Sunny, but these ideals have rubbed off on all the other members. Charlie eventually becomes as entitled as Dennis when he tries to talk to the Waitress.
Mac has also absorbed this overconfident nature and convinced himself that he and Dennis are more than friends. Frank is taken advantage of constantly after Dennis proves to the others that he is an easier target in his old age, but Dee has gotten the brunt of it. Dee calls herself the Golden Goddess and targets men in the same way that Dennis manipulates women.