LEON:
He realized that he loved you was when you smiled at him. Her bright smile that made his heart beat one million times faster and the way you cared and showed interest in him.
It's just that little things that made him fall in love since Ada didn't show any interest in him besides play with his feelings for her.
And it's also because you regularly check up on him and send him small gifts when he returns from a stressful mission.
CHRIS:
He realized that he loved you was when you showed him a few things about hacking that you learned from your father.
He couldn't help but watch you explain to him. To him your voice was angelic and music to his ears.
He had fallen for your charm and seductive side which you naturally had, without trying to made a huge Boulder punching man tank fall in love with you.
ALBERT:
He realized that he loved you was when he was staring at you while you were doing your paperwork.
He looked at your soft light pink lips, your focused eyes and your sweet innocent face.
Everyone said, making thee Albert Wesker fall in love with you, is impossible but with you, all it took was your hard work and innocence as you were not aware of his world saving plan.
PIERS:
He realized that he loved you was when you were training with him. To him training with you was like any other training session until he made eye contact with you.
Your eyes held determination and hope, and because he thought your eyes were pretty to look at then his knees went weak and couldn't bring himself to hurt you while training and called it quits for the day.
It made you confused but you were glad he called quits so that you could relax, it was your lazy day.
JAKE:
He realized that he loved you was when you two were at a shooting range. It was Jake's day off and what better way to spend your day off at a shooting range with your best friend.
Or thats what he thought.
He enjoyed the date, well he wouldn't call it a date, it was like a hang out to him. He had never had a crush or developed feelings for anyone during his hard past.
He looked over at his best friend as she shot a her target. He looked at her target and saw a hole in the center of its head.
A smirk formed on his lips then realized it might be very easy for you to kill him but that just made you more attractive to him.
Carlos:
He realized that he loved you was when you were playing with your dog in the park which he thought was the most peaceful and perfect thing he has ever seen.
You happily play with husky, unbothered by the inhumane lust of the Umbrella corporation.
A smile formed on his lips and he knew, he had to protect you at all cost.