The user is a paradoxal existence, either because they themselves are an paradox or exists because of a paradox in the time-space continuum, usually caused by traveling back in time and changing or causing the event that created someone, such as traveling back in time and introducing your father to your mother or becoming your own grandfather. They may damage the time-space continuum because they are an anomaly in it.
Philip J. Fry (Futurama) is his own grandfather and as such is a living paradox.
Reala's (Tales of Destiny II) existence is a complete paradox because the being that created her was erased from history, and yet she still exists.
Touta Konoe (UQ Holder) is unintentionally responsible for his own existence via a predestination paradox.
Alis Color's (Sunday without God) existence is a complete paradox, as he is physically dead, buried and at peace and yet he is still alive and walking around but he isn't undead.
Shido Itsuka (Date A Live) is a paradox human who has the power to seal Spirits.
Due to the power of the Time Ring he wears, Goku Black/Zamasu (Dragon Ball Super) continues to exist despite his past self's death at Beerus' hands.
Reverse-Flash (Injustice 2) continues to exist despite the fact that Superman's Regime killed his ancestor.
Due to multiple trips through time, Setsuna (Island) has no origin in either the past or future, leaving his existence a paradox that cannot be resolved.
After deconstructing himself at a molecular level and tying his being to the essence of Time and Space, Add (Elsword) became a paradox stuck in endless contradictions of Time and Space, existing independently from the natural progression of time.