How was the epic final battle of Avengers: Endgame actually filmed?

The answer

The Avengers: Endgame final battle was filmed during a special block of additional photography from September to October 2018 at Pinewood Atlanta Studios. The Russo Brothers split production into four simultaneous units, with each director commanding one unit while VFX supervisor Dan DeLeeuw and second unit director oversaw the others. Most of the heroes' actors were physically present on set for the iconic 'Avengers, assemble' portals sequence, standing together on a massive stage. The entire battle relied on 2,496 visual effects shots created by 14 different VFX companies. The film's total budget reached $356 million, making it one of the most expensive productions in history.