Any creature like Zealous Conscripts will allow you to make infinite creatures, Combat Celebrant does the same while also giving you infinite combat steps, and you can create a game-winning combo with it, Thornbite Staff, and Ashnod's Altar
Counterspell (Ice Age/Alliances, Tempest/Stronghold/Exodus, Masques/Nemesis/Prophecy) Counterspells are decent in limited, but by no means the be-all, end-all of the universe
There are a lot of characters from Snow White featured in Rise Of The Floodborn, including all seven dwarfs
Beating two opponents is easier than beating three
That means if you forget to tick up that counter in your end phase, forget to proliferate, or just miss something when an opponent attacks you, youre on your own