Which wizard duel in Harry Potter had the most impact on the series?

Iconic Wizard Duels
The Making of Harry Potter (2001)
Harry Potter
TV
Iconic Wizard Duels poll options
Iconic Wizard Duels
The Making of Harry Potter (2001)
Harry Potter
- Harry vs. Voldemort
- Dumbledore vs. Voldemort
- Harry vs. Draco
- Snape vs. McGonagall