REmake was the scariest in general by a long way, but RE2 had the scariest moment.
When playing through as the girl (after completing it with leon), there was this monster like nemesis that kept coming back. In one room (near the mirror room), I picked up an item, and he walked through the door! Thinking sneakily, I ran around him exited to the corridoor, which circled the room.
Just approaching the end of the corridoor, he jumped through the wall! Agh!
Never have I been so scared when playing a game as that moment. It was totally 'jump out of your skin' material, my heart felt it was going to explode. After taking him on, he fell to the floor, yet on leaving the corridoor there was an animation of him getting up and walking to the door.
The game promtly got turned off and has never been on since
That famous 'mirror room' jump was nothing on this beast smashing its way into the corridoor! Gives me the shivers just thinking about it.