Complain hard is a come back to anyone who uses that awful term try hard because all it means is they're trying to compensate that they don't try enough they don't do what it needs to succeed so they want to punish people for doing what needs to be done because they can't dare see someone having more determination than them to get better which is what it takes for even people with Talent they didn't just get good they had to practice so it's both a way to point out their contradiction and their insecurities.
The definition for complain hard is somebody that uses try hard to put someone down because they're actually trying to get better like they did. It's used to point out the hypocrisy and using the word tryhard for example let's say someone who has gone through what they needed to do to get there when you do the same thing they look at you like that's a bad thing and call you a try hard which is all that word really means that you're trying