Okay, for those that have zero social skills and don't understand subtle hints...
First, you don't want this guy as a friend any more? No problem. Everyone does this at some point and usually it isn't any big deal. People change and it never has to be someone's fault.
So for socially awkward dude: remove him from your social media contacts. Block his cell number, and do not answer any calls/texts you don't recognize. If he calls/texts you from a random number, block those too once you see who sent them (likely he might borrow a parent's cell or even landline if available).
If you see him out at a social event or randomly run into him somewhere: Polite by distant. Like a former boss you worked for at your first job. Say hello, ask him how he's doing and listen for a minute or two, and then excuse yourself and leave. "Hey, it's great seeing you, but I have to run/go to the bathroom/go talk to Sally." If he brings up being unable to contact you or the fact that you haven't answered his bazillion texts/messages - "Wow, never saw those. Weird." or "Yeah, I meant to get back to you but got really busy. Sorry!"
Any in person attempts to set up a future meetup: "Oh yeah, I have no idea if that would work. I'll have to get back to you about that." or "No, that won't work out for me, sorry!" excuse yourself (see above) and leave.
In the event he shows up at your house or apartment? You don't answer the door. Same thing as you don't answer the phone/texts. Keep your curtains closed if you hang out in a room that he might be able to peer into, but for the most part, check peepholes and avoid even speaking to him - do not open the door or acknowledge he's out there in any way. You did not invite him over, and it is not rude to not answer - he has no idea why you're home but not answering - and it is none of his business either. He'll go away after a few minutes. If he leaves a physical note, trash it.
What I think might be a good option B to consider in this case, is to tell him that you need a break from him to stop him from automatically contacting/texting you for a while. Tell him:
"Guy, I'm really swamped with work and life stuff at the moment, so I need to take a break from hanging out or talking/texting with you. I won't be responding to any texts/calls from you, and I do not want you to come over to my house. I will let you know when I'm ready to reestablish contact with you."
If he asks/questions why, then some form of response like this: "As I said, I am quite busy with work/life stuff, so I need to cut way back on social interactions. I think it is best if we stop all communications/socializing until I am ready to try again."
And if you're feeling real generous, you could throw in something along the lines of: "You are one of the people that tend to text me quite often and also not understand when it is time to leave when visiting, resulting in me getting behind on things I needed to get done around my house unless I stay up late to do them, resulting in loss of sleep time, which causes issues at work the next day." and add back in that the work/life issues are of importance so no more contact until you let him know.
This accomplishes two things:
1. You're alerting him up front and in no uncertain terms to stop contacting you in any way. As he is socially tone deaf, this is NOT being rude; it's being polite and no-nonsense, speaking to him in precise language so he does understand you. Without very clear, factual instruction on this, he will not understand and could continue to annoy and harass you for months. There is an added bonus that he may think about what you've said and start trying to self-regulate his social interactions a bit more with any unfortunate person that is too afraid to say anything to him about this.
2. You are making it clear that you are the one that will reestablish contact with him. He will not get anywhere with you by continuing to text you or dropping by your place.
Follow the first part (no contact stuff - block number/don't answer door/polite but distant when meeting randomly) as necessary going forward.
He may react poorly to this; say you hurt his feelings, call you rude, whatever. But here's the thing. You aren't being rude. You are establishing a boundary. As it is a boundary he is used to abusing, you may get some push-back, but that's why you just stay polite and firm and end the contact with him.
Being polite doesn't mean being a doormat. "No" is a complete sentence. Anyone that calls you rude or mean for that (as long as you aren't spewing expletives and arguing with them) is really just trying to manipulate you into allowing them to walk all over you again. It takes a while to develop a polite spine, but this is a good way of doing so. Either do the slow fade, or tell the guy you're going no contact politely but firmly, block him and treat him like running into your middle school vice principal if you see him out in public.