I Brought a Sniper Rifle to the Cultivation World

A mercenary transmigrates to a low-martial fantasy realm and wastes no time shooting an immortal dead, earning a God-Tier Marrow-Cleansing Pill. After swallowing it, his martial talent becomes the best in the entire star domain. To avoid being ambushed and killed by immortals, he resolves to cultivate martial arts and strengthen his body so he won't be taken out in one hit. As long as he survives the first strike, he'll have a chance to draw his gun and fight back. Along the way, whenever he runs into someone he can't beat, he fires a shot to settle things. If that doesn't work, he fires another.