Freesound - Flawless Victory Game Over (deep voice) by Audeption

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Top 6 FREE Vocal Plugins

Game Over Sound │ FiftySounds

Best Space Marine Voice Changer [2023 Updated] - EaseUS

Evolution of Flawless Victory Sound Effect (1992-2019)

GAME OVER VOICE, GAMING SOUND EFFECTS

Deep Voice: Game Over [00:11] royalty free audio

Volitions by Venus Theory (Free Edition) - decent

It looks like Behringer's free DAW will come with free VST synth plugins that integrate with their hardware counterparts

Game Over Sound │ FiftySounds