Tetsuko Umezawa, Fugitive
Oracle Text
Creatures you control with power or toughness 1 or less can't be blocked.
Card Rulings
4/27/2018 Once a creature you control has been blocked, changing its power to 1 or less won’t cause it to become unblocked. Changing its toughness to 1 won’t cause it to become unblocked, and changing its toughness to less than 1 will cause it to die.
Cephalid Constable, Mistblade Shinobi, Riptide Entrancer, Riptide Pilferer, Rootwater Thief, Scalpelexis, Soul Seizer...
And that's not counting all of the Ophidian variants out there. Fun for tiny commanders and a fun commander in general... not to mention the lore significance.
Power or Toughness of one. Frail elementals like Frost Walker and all KINDS of red stuff if you're running it in an izzet deck.
Bloodforged Battle-Axe just found a new home.