Deontay Wilder Denies Assault Claims From Ex-Fiancee's Son

Deontay Wilder says his ex-fiancée Telli Swift's son's allegations that the boxer brutally beat him up are totally bogus.

Deontay makes a vehement denial in new legal docs obtained by TMZ ... and his legal team goes even further ... claiming, among other things, if Kerron Swift suffered any injuries, those were caused by pre-existing conditions or unrelated events.

In addition ... they say that Kerron cannot back up his claims of emotional distress, false imprisonment, assault and battery.

TMZ Sports reported earlier ... Kerron said Deontay slapped him when he was 13, and in a separate alleged incident, beat him with a belt until he was bruised.

Kerron also claimed Deontay grabbed his throat before throwing him around "like a ragdoll."