General

ive been seeing alot of hot fat guys in my lecture halls, and like roaming around campus n shit but im scared that if i approach them they’re just going to think that its bullying, or a dare, or a prank or something. like the “asking people out as a joke” type thing. which obviously its not, but due to my appearance and the company that i keep it might come off that way. the only fat(ish) guys ive been able to talk to have been slightly chubby guys ive met through frats, or mutual friends who know im into bigger guys and have set me up with them, but otherwise im really scared to approach them on my own, not because im afraid of approaching people because thats effortless to me, but because im scared that they’ll assume i have malicious intentions

I do believe any male always apreciate any girl who initiate the talking first. Either he thinks you have malicious intent or not, its up to him to decide, we can't control that one. As long as you consistent approaching them with good intention, I think he would believe your true nature eventually (in good way ofc!)

Don't do it while they're eating, and try to avoid it in open spaces with a lot of people. Especially good if it's just you and him in a quiet corner- because if he does think it's a prank, he'll look for onlookers.

Good points so far. I'm assuming you want to get to know the guy better, he's a little awkward, and usually not around women (as for the outgoing fat guys you don't need to worry too much about them being insecure).
Since I've been in the position myself, some suggestions from my perspective: start with a friendly, non-flirtatious platonic chat. That way it's less likely he'll assume you're joking or feel overwhelmed by your directness. If he's needy or inexperienced he may assume your chat to be flirting - but in that case it's a win for you anyways.
A platonic chat will help you get to know him and if he's a raging incel (not too unlikely with the other factors). If you still like him after chatting a bit, you can slowly turn up the heat. Always be honest, but not too fast, as he may be overwhelmed due to being inexperienced. Telling him "I like you, we should date" in a direct manner may actually be a smart move, but make sure to make him suspect this will come from you way in advance and give him time to think about his reaction.