Fire Lord Azula | Narset's Reversal | Tidal Barracuda (and one other card)

Cards

Narset's Reversal and
Twice Upon a Time // Unlikely Meeting in hand.
Fire Lord Azula and
Tidal Barracuda on the battlefield (
Fire Lord Azula without summoning sickness).

An opponent cannot block and kill
Fire Lord Azula You control at least two Doctors.

({2} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) each other turn available.

Declare
Fire Lord Azula as an attacker, triggering its firebending ability, adding ({R} magic symbol) ({R} magic symbol) .
Holding priority, cast
Twice Upon a Time // Unlikely Meeting by paying its mana cost.
Fire Lord Azula's second ability triggers, copying
Twice Upon a Time // Unlikely Meeting.
Holding priority, cast
Narset's Reversal by paying ({U} magic symbol) ({U} magic symbol) , targeting the original
Twice Upon a Time // Unlikely Meeting spell.
Fire Lord Azula's second ability triggers, copying
Narset's Reversal, targeting the original
Narset's Reversal.
Resolve the copy of
Narset's Reversal, causing you to copy
Narset's Reversal targeting the original
Twice Upon a Time // Unlikely Meeting spell, and then return the original
Narset's Reversal to your hand.
Resolve the copy of
Narset's Reversal, copying
Twice Upon a Time // Unlikely Meeting and returning the original
Twice Upon a Time // Unlikely Meeting to your hand.
Resolve both copies of
Twice Upon a Time // Unlikely Meeting from steps 3 and 7, causing you to take two extra turns after this one.
Repeat during your second extra turn.

This combo has been estimated to be Ruthless (Bracket 4+).