What is in your opinion the scariest/ strongest deck and/or deck strategy in a non cEDH table?

We're not just talking about the potential potency of a commander but rather about a fully fleshed out deck with a solid plan, the ability to stay online despite moderate disruption, good card synergy, a form of alternative win cons and a good mana ramp engine. No matter whether you own that deck or not, what's the one that would surely scare a table?