Living at home with parents at 40 doesn't make you a failure, but the reason you're living there might. If you tried and failed at something and had to move home for financial reasons, fair play - whether that's trying or failing at business, or trying and failing to make a relationship work. If you never tried at all - saw not reason to live independently, or fucked up your own relationship - that's a failure I suppose.
If a man doesn't have friends or hobbies but understands why they are important to his partner and fills his time productively in other ways, he's not a failure. If he lies around all day getting depressed without doing a thing about it, and is an energy vampire when it comes to his partner - he's a failure.
'Being successful' depends on your measure of success, and mine isn't financial. Being low paid doesn't make you a failure.
My red flags over and above violence, racism, intolerance and the like are selfishness - a man who puts his needs above everyone else's every time - and laziness. I personally cannot stand a man that lacks ambition - but it doesn't mean he's a failure. Just not an energy I can vibe with.
The only out and out unambiguous failure I can immediately think of is not showing up for your kids - not seeing them, weaselling your way out of paying maintenance. Everything else is either a character flaw, a crime or depends on the circumstances, not a failing as a 'man'.