If they are at full health they will just barely survive. I played against a Titan yesterday, I used golden gun he FOH he survived. When I respawned he killed he with shoulder charge. Happens when I play my friends in rumble to.

If he had skull fort (I think) that's why. But I play a Titan and have never survived a golden gun shot even with my resistance on during FoH. It's this beautiful thing called 'client side hit detection' and the fact he was probably on the edge of your GG range.