The scene after Cyrus gets shot and the police raid the gang meeting. It's complete chaos with hundreds of people running left and right in a panic, shoving each other, fighting with the cops and trying to escape. Rembrandt, indicated to be the youngest of the Warriors, becomes separated from the others and is shown pressed up against a wall trying to avoid being knocked down by the crowds, until Fox manages to find him and gets him out. For anyone with claustrophobia it's even more uncomfortable.
The mood of ominousness comes when the DJ broadcasts a threat to The Warriors after Cyrus' murder.
DJ: Alright, now. For all you boppers out there in the big city. All you street people with an ear for the action, I've been asked to relay a request from the Gramercy Riffs. It's a special for the Warriors. That's that real live bunch from Coney. And I do mean the Warriors. Here's a hit with them in mind. (Cue Arnold McCuller's cover of "Nowhere To Run (Nowhere To Hide)".)
The Warriors hiding from the Turnbull ACs, who are driving around in a bus armed with metal pipes, wooden planks, poles etc. The audience knows they're after the Warriors, and although they don't know this they quickly realize that the truce is probably off. To make it to their train, they end up having to sprint down the street as Turnbulls chase them in the bus, screaming and swinging weapons at them, and the Warriors only just escape.
Fox's death. He gets tackled by a police officer in the subway and fights with him, yelling for Mercy to run. During the struggle, the cop shoves Fox away and he falls off the platform onto the tracks, right as a train comes hurtling along. That is not a nice way to go and it would be horrifying for everyone who witnessed it. None of the Warriors know what happened to Fox either and they don't have time to go back looking for him; based on Mercy's account they probably spent most of the night thinking Fox was banged up in a cell somewhere, not realizing his mangled corpse was lying on a subway track or in a morgue.
The Baseball Furies. You're running for your life in the middle of the night in New York City and you come across a gang of creepy, face-painted mutes wielding baseball bats coming towards you....
There's something highly eerie about the leader of the Punks stalking Swan through the empty subway station, the only sound being his rollerstakes scraping along the floor. And then more of the Punks start showing up and just hang around, watching Swan silently. He later reveals to Mercy that he realized they were following him and was trying to play it cool while he figured out what to do. Both scenarios are creepy as hell: either being unknowingly followed by someone who plans on hurting you, or knowing you're being stalked and there not being anything you can do about it but wait.
The famous scene where Luther taunts the Warriors by clanking beer bottles together and chanting "Warriors, come out to play" over and over, sounding more and more deranged each time. It may sound silly on paper, but it's surprisingly unnerving in the film itself, driving home just how unhinged Luther is (as if it weren't obvious already by this point).
to The Warriors after Cyrus' murder.DJ: Alright, now. For all you boppers out there in the big city. All you street people with an ear for the action, I've been asked to relay a request from the Gramercy Riffs. It's a special for the Warriors. That's that real live bunch from Coney. And I do mean the Warriors. Here's a hit with them in mind.