In addition to using professional software like TikTokABC, there are other ways to download TikTok videos without watermarks. They include:
screen recording: every smartphone or PC has screen recording software. Play a TikTok video and put it on your phone or PC screen.
video editing software: watermarked videos can crop the watermark or remove it by editing using the repair tool. But this may cause the video quality to decrease and affect the video quality.