... says every small time villain ever.
Not being able to see your own faults is the worst mistake you can make. It prevents you from improving and it makes you project all your shortcomings on others, leading to needless conflicts with people much better than you.
Not bad, he neither becomes arrogant through success, nor discouraged by failure.
How do you know that he won't be discouraged by failure? This guy hasn't failed at anything yet.
Worse yet, he has not encountered anything remotely challenging, even as he faced higher level opponents.
Even an abyssal demon (though a weak one by abyss standards, apparently) invading the test zone was not a danger to him.
So, "nor discouraged by failure" is just baseless.