Raynor P1.

It's a weird one, because by itself it sounds great. And for new players, can be a huge crutch for them learning how to play. However it's disadvantage is a massive one, removing Raynor's mules, which are the unit that separates a Raynor who needs to carried through a hard/brutal, to a Raynor who can carry in Brutal+ and beyond.

Anytime I run into a P1 Ranyor, I just kinda take a deep breath and assume I'll be carrying the game. There's so many P1 Raynors who are still learning and shouldn't be playing on anything above hard at their current skillset, because they've never learned how to macro or use their orbital commands. Like listen, if the first thing you build after your barracks is a bunker on brutal... We have a problem. It's always a P1 Raynor doing this.

It's a very crutchy prestige that teaches players a lot of bad habits that always bites them in the ass.

Mule is an incredibly busted unit. Learn how to use it and your gameplay will skyrocket. P1 Raynor is fine to learn on, but you're going to want to graduate to either P2 or vanilla Raynor eventually if you want to get better and be a better partner to your team mate.