I like the episode where Mordecai and Rigby first got their jobs at the park. When Benson first met them, he asked them politely not to make a mess in the kitchen. At first, Benson wasn't aware of them being jackasses. Until a never ending rock, paper, scissors game almost caused destruction to the park and Benson had his first yelling out at Mordecai and Rigby and completely losing his trust for them.
And another wild episode was when Pops ordered Benson not to yell at Mordecai and Rigby anymore or else he'd be fired. Benson tried hard to be very patient with Mordecai and Rigby, but they kept doing reckless things which caused Benson to bottle up his anger, creating a powerful storm almost destroying the park, until Pops gave him back permission to yell. And Benson let out his most powerful yelling attack at Mordecai and Rigby causing them to go deaf. And at the end Benson told the two to clean up this mess or they're fired in a calm happy voice.