Although she is a cost seven card, Gramma Tala can be shifted into the game as early as turn five if you have another card of the same name on the field
6 Najeela, The Blade-Blossom Doesn't Need A Partner To Go Off 5 Najeela was created for Battlebond, a set intended to be drafted and played as a Two-Headed Giant game with a partner
Trickster's Elk You want to say Trickster's Elk is like removal, and granted, switching off the busted activated abilities on a key creature is impactful in a singleton format, just make sure you don't care about your opponent controlling a non-flying 3/3 because you might accidentally improve an opposing creature with +1/+1 counters
Additionally, creatures with infect can hypothetically deal with indestructible creatures, as enough -1/-1 counters can still destroy an indestructible creature
Fortunately unlike digital card games, you can proxy (use a paper card) when you are just screwing around with friends