Agamemnon is the general of the Greek army and Menelaus' big brother. Sounds impressive, right? Well, Shakespeare cracks a joke about how unimpressive Agamemnon really is when Aeneas shows up at the Greek camp looking for him. Remember what happens? Aeneas makes a big, elaborate production out of asking some guy if he can speak with "the high and mighty Agamemnon," or "that god in office, guiding men" (1.3.231-232). It turns out that Aeneas happens to be talking to...you guessed it... Agamemnon.
Hmm. We guess old Agamemnon doesn't exactly look like a "high and mighty" "god." Otherwise, Aeneas would have recognized him.
It's not that Agamemnon is a bad guy. He's just an incompetent leader. (If you ask us, Ulysses is the real brains of the Greek army.) Agamemnon doesn't quite understand why the war is taking so long and offers up some pathetic (albeit fancy) speech about how the gods are trying to test the Greeks before they let them win the war (1.3.1-54). Ulysses has to step in and point out that, actually, the problem with the Greek army is that they've got zero respect for their general and commanders.
But with a guy like Agamemnon, can you blame him? By the way, this poor guy has an awful fate in store for him back home.