When you're editing (or reading feedback from your betas), you'll get a lot of comments about your main character. One of the big concerns with readers is whether or not your protagonist is someone the reader wants to spend a whole book following.

No. People love plenty of characters who aren't all that likable. Just think of villains. They're often evil and yet many of us still find them lovable! Many of us enjoy a 'good' villain or antihero, even when they become the MC.

Heck, many people have a different definition of what is likable vs what is a readable character. Many of us have different standards of how much we will and won't tolerate.

Absolutely. When we like people, places, or things, we start to get invested in them, usually more quickly and more easily than if we start out hating someone. Especially in first person stories, you'll hear plenty of readers comment that they just didn't like the MC, so they stopped reading or couldn't get into it. It's a very common reason for putting a book down.

Think about how many times you've heard someone saying something along the lines of, "I couldn't get out of chapter one. The MC was so bratty/snobby/annoying/grating/etc.

Don't be over-the-top. Characters that are over-the-top are very often some of the most difficult to have as a protagonist. They often make for interesting side characters, but as a lead, that one unique trait or dimension can be an extremely polarizing force. Consider for example, some comedy movie actors. Sometimes those characters work as leads; very often you get a large group of people who are just annoyed by the constant over-the-topness.

Be relatable. Maybe your protag is kind of a jerk, but he gets cut off on the highway and he says what many of us are thinking when that happens. Maybe we don't react the way your protag does, but we've all been there. Sometimes what we relate to is a situation (being cut off), other times it's a character (for example, in Run Cold, a few people can relate to having an overbearing parent), or an interaction (talking to our crush or dealing with an angry customer at work) or something else varied and small.

Be human. People aren't perfect. We make mistakes and do all kinds of crazy things that get us into and out of trouble. We hurt and hinder and help ourselves. In writing, you generally want your character to keep digging themselves into a hole without too many early victories, and introducing human elements can really help that. Being human makes us complex. Being human makes us interesting. Don't be afraid to let your characters show a little humanity now and then. Let your protag do the illogical thing and lie to their bestie about where they've been because they think they're protecting them somehow. Let your tough guy rescue that puppy and take night classes to get a better job.

Be three-dimensional (sort of). You're writing, so you can't have your character actually pop off the page, but you can give them multiple dimensions and facets, both to their personality and situations they find themselves in. People aren't usually just one adjective or mood or experience; most of us fly through a bunch of different reactions on an hourly basis.

For example, when you wake up to an email from Wattpad asking to feature your story. You're so excited you accidentally forget to take your math project in to school, and the teacher marks you down a full letter grade. You needed that A to make sure you got a B- grade on your report card. Now your parents are going to see a big "C+" and you'll be in deep trouble.

Already you've got different feelings, reactions, and stresses. Don't forget that your characters go through these swings, too.

Often, the more dimensions you add (within reason), the less predictable the character becomes, and the more a reader wants to find out what happens. If we know that Bob is always going to do what's right, or that Phil will always do something bad, that's okay, but it isn't often very grabbing. Now look at Charlie. Charlie has done good and bad things. We think we know what he'll do, but we aren't really sure, and when we aren't really sure, we keep thinking about him, and that makes us want to read on and find out what Charlie actually does.... Charlie has involved us in the story.

Be compelling. Maybe your protagonist isn't that likable. Maybe he's just sort of a quiet observer of everything and everyone in the story. But what if he's got this super awesome job? What if he's in this wild situation? What if the plot has so many twists, turns, and mysteries that it outshines your protagonist? That's okay. Sometimes when you have a tough-to-love protagonist, you can still have a great story because everything else is so good your readers love it anyway, which leads me to my last point:

Write a goddamn fantastic story.