The creature kill is relatively fair and broadly very useful
It also combos well with another card on this list, Pyrohemia, turning every one point of damage into a +1/+1 counter
Any iteration of Aurelia, the Warleader, or Tajic, Blade of the Legion, or most any decks who want to turn sideways as fast as possible could use Reckless Stormseeker to make sure their armies get there and get there fast
For example, if two creatures you control with lifelink deal combat damage at the same time, Sanguine Bond's ability will trigger twice and you may choose a different opponent for each trigger
Plus, activating her commander ninjutsu ability will only ever cost one blue and one black mana, as commader tax doesnt affect abilities
Then in your upkeep if you have 20 or more you win that game