Venkman's attitude and demeanor towards him was pretty much the straw that broke the camel's back for Peck.

Peck had it in for the boys from the get go. He viewed them as con artists. While I don't think Peter was the best choice in dealing with people (quite a jerk and not the ghostbuster I idolized), he didn't bring this on. Peck was there to start trouble from the get go.

It's a little bit of both, I think. On the one hand, Peck had it in for them (check his behavior at the Mayor's office) but on the other, I think Venkman's attitude genuinely rankled.

Then again, at their first encounter, Peck asks a lot of snide questions–“How many ghosts have you caught, Mr. Venkman?”

I submit that Peck was a frustrated, possibly dead-end, bureaucrat looking for someone to knock down so he could seem to stand a little taller in comparison. I suspect he was the kid in high school who got his @$$ handed to him on a daily basis. This resulted in a “I'll show them!” attitude that, frankly, annoyed his superiors at the EPA to the point where they basically just dumped busy work on his desk to keep him out of their way.

In the final analysis, Peck was a monster tool looking for a fight. He just happened to pick one with a guy who had very little patience for such @$$holery.

IMHO, but I could be wrong, it's been known to happen.

RealmMan;162678
I submit that Peck was a frustrated, possibly dead-end, bureaucrat looking for someone to knock down so he could seem to stand a little taller in comparison. I suspect he was the kid in high school who got his @$$ handed to him on a daily basis. This resulted in a “I'll show them!” attitude that, frankly, annoyed his superiors at the EPA to the point where they basically just dumped busy work on his desk to keep him out of their way.

That's an interesting way to analyze his character. Does the GB novelization shed such insight into his backstory?

Slime Lord;162680
That's an interesting way to analyze his character. Does the GB novelization shed such insight into his backstory?

Taken from page 185 in Ghostbusters: the Supernatural Spectacular

Walter Peck was feeling the self-satisfaction of a man who was about to get revenge on an enemy, and he wasn't entirely sure that he liked it. Revenge wasn't the point, he told himself. I'm a public servant, looking out for the public good. What I do I do out of responsibility, duty, and the law. I don't do it because I like it; I do it because it has to be done. Having told himself all of these things, he at last permitted himself a thin, sneering smile. Duty or not, I am really going to enjoy sticking it to Peter Venkman.

Sounds like he felt he had a job to do and wanted to enjoy doing it.

I think it's kind of stupid that Peck ended up winning in the end. I'm surprised that the Mayor didn't defend them when they were being sued.

Well, did he really win? He gets thoroughly humiliated in the Mayor's office, the Ghostbusters end up fully vindicated in spite of his efforts, and he gets a ton of melted marshmallow dumped on top of him just to add insult to injury. And in his sole RGB appearance, he's embarrassed even further.

not to mention humiliated at every turn when he tries to shut down the Ghostbusters in the game.