I watch a lot of TV. Mostly because I like having the background noise while I'm working, but occasionally I will pull my attention away from whatever I'm doing and watch whatever's on. My weakness tends to be the procedural-type shows, because I'm a sucker for a good mystery.
There's one thing I've noticed, though. The writers really, really don't like it when their characters lose. Their typical protagonist will casually go about their business with gaping bullet wounds and broken bones. They're abrasive, but their boss doesn't care, because they gets RESULTS, dammit. They easily outsmart the murderers and their convoluted plans - and if this is an amateur sleuth or a brilliant consultant, the actual police will just look on with their mouths agape. And if it seems like the antagonist HAS gotten one over on our hero, it will secretly be part of the master plan, and it will be revealed in the last ten minutes that the hero was only pretending to be vexed.
This is your garden variety Boring Invincible Hero - and while the example above is from your typical TV procedural, you'll find iterations in every genre. These characters can be fun to watch sometimes, but I can't think of the last time I ever really related to one of them. I think it's definitely possible to write a larger than life hero who the audience can get invested in, and there are great examples out there (my overpowering love for Sherlock Holmes is well-documented), but that aspect alone isn't what makes a character appealing.
I always joke that I can't fully fall in love with a character until they fail at life a little, but there's a lot of truth to that. If there's one thing that the Boring Invincible Hero illustrates, it's how important it is for the audience to see a protagonist really struggle, both physically and emotionally. Without that struggle, the character just sort of glides through the conflict without truly becoming a part of it. If we can't get into their heads and see how terrified or furious or insecure they are, there's no real weight to their victory.
So no matter how much you love your protagonist, don't let them become a Boring Invincible Hero. Let their flaws get them into trouble, and don't let them get out of it easily. Let their relationships be brutally difficult once in a while. If you give them an injury, let it weigh them down. And show us what they care about the hard way. To paraphrase Donald Maass a bit, think of the experience you want to avoid putting your character through. What would happen if you put them through it?
That's all from me today. Happy writing, everyone!