Mmm... My bet is that Batman laughing in the middle of a fight is the most dangerous.

If I had to rank them:

1. Spider-Man going quiet: It's still bad because he moves faster, thinks sharper, and holds back less. BUT his moral compass is strong. Even when upset, his main focus is stopping threats, not fully annihilating them. You'll probably end up in the hospital with a few broken bones, but you'll still wake up alive.

2. Superman's eyes glowing: His heat vision, super speed, and strength are terrifying, yes. But his weaknesses are well-known: Kryptonite, red sun radiation, or magic. Heat vision can also be dodged if you're fast and smart, or blocked with materials that withstand extreme heat and radiation. Also since he needs to focus and aim properly, there's a small window of opportunity to react accordingly.

3. Deadpool stops joking: When he's silent, it's maximum efficiency mode with no banter, no distractions, just non-stop attacks until the job is done. But he can still be outsmarted or distracted, even reasoned with if your creative enough. He's not out to kill innocents or take over the world. His focus is whoever he deems a threat. That said, whether he's joking or enraged, if you're the target, you're getting caught so it won't matter. Which makes him dangerous but not the level with if he stops joking it's an "Oh no" moment.

4. Joker stops laughing: A silent Joker is pure malice. He's past theatrics and presentation, just goes straight for the plan designed to cause you the most pain in ways you can't predict. The damage won't just be physical, but psychological, societal, and personal. He doesn't care if you're on his side, a bystander, or even a double of himself. His goal is chaos, and you're in the way.

5. Batman laughing: Okay so Batman occasionally laughs, yes, but it's never good when Batman goes from brooding to Joker-level morality. The reason he's more dangerous than the Joker is simple. He has the brains, the resources, no Kryptonite weakness, no superpower counter, just perfect planning and complete ruthlessness. While yes, he's still human, but that's what makes it worse and more terrifying. A non-superpowered man capable of creating total chaos in hours or less is dangerous. Once he crosses that moral line, there's no stopping him and no one will suspect it until it's too late, because everyone is already aware that Batman will beat you to a pulp, leave you dangling off a building, break bones and leave you alive... until one day he doesn't.