Practice the "Gas Boost" (holding Space while hooking) to reach the speed required for one-shot nape kills.
If you want to improve your kill speed without risking a ban, focus on mastering the Official Equipment and game mechanics: Attack On Titan: Evolution Script – Auto Kill
Downloading script executors or "no key" scripts from unverified sources can expose your computer to malware. Practice the "Gas Boost" (holding Space while hooking)