Why couldn’t Karna defeat Abhimanyu? Abhimanyu did not possess all astras that Karna had in any case.

Why couldn’t Karna defeat Abhimanyu? Abhimanyu did not possess all astras that Karna had in any case. Who said abhimanyu doesn't have astras. He had enough astras to beat all kaurava warriors. Although he didn't have vasavi shakti but no to forget karna can only use it when his life is in extreme danger and he had reserved it to Arjuna. Now about karna not defeating abhimanyu. It's simple abhimanyu was a better warrior in skills ,speed as well as swiftness. Plus he was courageous enough to refuse to retreat. Karna always retreated from battle when he found himself overpowered or in difficult situation .Karna was beaten back to back by abhimanyu atleast 5 to 6 times inside charavyuha and badly wounded. When karna went to ask drona how to defeat him drona clearly said abhimanyu is courageous and fights like a tiger. Drona said he has immense skills,courage and speed. Also Arjuna had taught him kavacha dharan Vidya a method to tie armour in such a way that body is protected from every end which was taught to Arjuna by drona himself. In final abhimanyu was a better warrior than karna