companion, buddy, teammate, colleague
Si quiere que se case con otro compañero.
If he wants her to marry another colleague.
— Kajaki (2014)
Demonios, parece que tendrás explicaciones que dar, compañero.
Damn, looks like you'll have some explaining to do, mate.
— El Maquinista (2004)
Tenía olvidado completamente a este compañero.
I had completely forgotten about this colleague.
— Nausicaä del Valle del Viento (1984)