Breaking up is hard to do, as 2GetHer once said. It's not just getting broken up with that sucks, but breaking up with someone else is just as hard, if not worse. As we all know, most bros have problems facing rejection. So trying to break up with a bro that doesn't want to is hard. Like, making the bro who has your sexts in the cloud hate you might not be the best idea. If you're not about that revenge porn life but you still want to break things off, just make like Leonardo DiCaprio and incept his own breakup.
The key to getting him to agree to a breakup is low-key acting like you're already broken up. I mean, the number one rule of getting a job is to act like you have the job. Like remember at the start of Gossip Girl when Dan's mom just peaced out and Rufus was left in Brooklyn running her art gallery? I mean, obvs we don't mean abandon your family, but you're not married and you don't have kids, so it's totally acceptable for you to separate yourself without dissolving your relationship status. Take a vacation or go out of town a few weekends in a row without him, which will start putting literal distance between you two. Or tell him you're about to get really busy at work and then stop texting him for a week.
The distance will make him realize he can actually live without you, and the fact that you aren't missing him will be a major hint he isn't the Ryan Gosling to your Rachel McAdams. Then, when you do hang out again, tell him that you think spending time apart was actually refreshing. It's a soft breakup because he already spent a week without you, so when you finally get rid of your title, it won't be that hard for him to move on.
If you haven't been dating more than a few months, you can also just bore him out of wanting to date you. The next time you guys go out, don't engage in anything particularly interesting, and do something boring like watch a movie where you don't have to actually talk.
Obvs you're not a total ice queen so you're not going to be actively mean to him. You just want him to realize that he's not right for you. So if being boring and distant doesn't work, just be yourself. Because your true self isn't into him, and nobody likes dating someone that isn't into them.
You can also slip in that you're on the rocks in conversation to incept the idea of breaking up. For example when you're at the mall you might say, "I wonder if we're having trouble finding a parking spot because the universe can tell we're on the rocks" or "So my boss thinks we're on the rocks because I'm spending too much time at work." You know, keep it subtle.
At this point if he hasn't already broken up with you, he'll ask you what's going on. Now that he's noticed something's wrong, you can agree with something like, "Yeah, I noticed it too. I feel like we hit a wall." I mean, he might feel like you're attacking him like a three-way call, but if you talk about your relationship using "we" and "us", it'll feel more mutual to him when you actually break up. Or blame it on your friend with something like, "Becky thinks we should break up. She noticed both of us are unhappy and I agree."
If all this doesn't work, just tell him you get the sense he wants to break up, and you totally agree. Major inception. Plus bros love being right, so how can he disagree with that?