We only see a image of this mysterious group in Rey's force vision. He killed them all, and became the Master of The Knights of Ren. Kylo Ren is very experienced, and has eliminated all competition. I may remind you that Kylo Ren slaughtered all of Luke's apprentices with his lightsaber. One might dispute these claims, because of his defeat with Rey. Lightsaber Combat- Kylo Ren is extremely skilled in lightsaber combat. Yoda, Mace Windu, Obi Wan, Anikan, and Darth Maul have never been seen to manipulate the force like Kylo Ren has. These abilities have never been seen before. He is able to read minds, and torture them. He is also seen as very advanced in torturing his opponents through the force. He stopped a laser from hitting him, and immobilized Poe. In the beginning of Force Awakens, Kylo Ren abuses the ability of force immobilization to defeat his enemy. This is already understood, because his grandfather had the highest midichlorian count ever. Kylo Ren is extremely powerful with the force.
Force Abilities: Most of this content will be coming from Canon sources.