When a character in a video game has dialog - is it (V.O.)

VO

BECAUSE

the video game person isn't a REAL character, the lines can be dubbed in a sound booth, AND it's coming from an external source.

I would suggest labeling the character VIDEO CHARACTER,

OR

You could avoid the issue by naming the character GAME VOICE, oh, oh oh,

Think of Kit from Knight Rider.

How much of a character IS this character?
Name and write accordingly.

Yeah, V.O. if it's coming from any electronic source, phone, radio, TV, computer, video game, etc.

GAME VILLAIN (V.O.)
Come no closer unless you are
prepared to die!

GAME HERO (V.O.)
Your mama wears Army boots.

V.O. fight noises, punches, grunts, gunshots -- then a giant explosion!

NERDBOY
I won, I won! Take that, Baron
von Evilheart! Yay me! Whoo!

-Derek