What do you consider to be the peak battles in each season?

For me it would be

Season 1 - Shu vs Lui,
 Valt vs Quon
Valt vs Zac
Shu vs Wakiya 
(all in the Nationals)

Season 2 - Shu vs Valt finals
 Daina final battle vs Joshua
Cuza vs Kurtz (that one had great buildup too)

Season 3 - Aiga vs Suoh (longinus cup finals, best burst finish in the entire franchise imo)

Free vs Kyle (god-tier animation)
Valt vs Hearts (overall the best battle objectively speaking)

Aiga vs Phi final was too insane

Season 4 - Drum vs Joe
Delta vs Blind

---

yeah I agree with all those

What do you consider to be the peak battles in each season?

For me it would be

Season 1 - Shu vs Lui,
 Valt vs Quon
Valt vs Zac
Shu vs Wakiya 
(all in the Nationals)

Season 2 - Shu vs Valt finals
 Daina final battle vs Joshua
Cuza vs Kurtz (that one had great buildup too)

Season 3 - Aiga vs Suoh (longinus cup finals, best burst finish in the entire franchise imo)

Free vs Kyle (god-tier animation)
Valt vs Hearts (overall the best battle objectively speaking)

Aiga vs Phi final was too insane

Season 4 - Drum vs Joe
Delta vs Blind

I like drum vs blind as well as all of those. Shu/free vs phi was pretty good too.