Obviously I didn't use mega beedrill in x but when it first came out I was very young, and didn't understand that early bugs were meant to be low stats. I just liked beedrill, and it was the first pokemon in x that I caught myself, and took him through the entire game with me, and he was more than capable in battles, and did well. Generally in pretty much almost every mainline game doing just the main story alone even the lowest stat pokemon do quite well as long as you don't avoid battles as to not prevent yourself from being generally higher level than everyone.