At best,basic scientist can two shot you if he can aim well. I doubt anything can one shot a 125 health character right now (closest to that would be a fully charged headshot from future cactus with damage upgrade followed by any shot from him)
I don't believe the Scientist has the ability to one shot for 125. Are you sure it wasn't the Foot Soldier? As at times they can look alike.
The ZPG rocket can one shot a target for 125. Also on the plants side Kernel Corn can hit for 300 with his shuck shot, and Super Brainz can hit for 120 with his super ball.
