Negataneous 

To happen instantly in the past

The dinosaurs negataneously disappeared.

Negataneous by Logan D. June 13, 2011

Negatatious 

An urban gentleman that’s known in his hood for being negative.

Leroy don’t wanna go…Again! Damn that boy is always negatatious!

Negatatious by Atari Deets December 20, 2021