Well, he is spoiled and he is stupid, so she's not far off the mark there. He was an emotionally-stunted mess and had been ever since Snoke had latched his claws into his young mind. He doesn't pay heed to anything she is saying until she calls him weak. That right there was the chink in his armor. It was what Ben Solo had feared, and deep within himself, Kylo Ren feels the same way. He is afraid, so afraid that in a family full of people that did things straight of legend and who shone as bright as the stars, that he was only mediocre in comparison.

"I am not weak!" He practically screams the words out in a fit of rage.