Josh Allen was all in on his fiancée while out at a "Sinners" premiere party Monday -- supporting her endlessly at the big movie event ... and even planting a kiss on her too!
The Buffalo Bills superstar traveled to Mexico City to show love to his soon-to-be-wife as she promoted her new Michael B. Jordan flick ... and he played the role of doting partner extremely well.
The footballer -- who rocked an all-black 'fit for the occasion -- watched her shine on the red carpet from afar .