Deriving from the ancient Greek words "hell" and "fat", hellafat has become a colloquialism expression of seniority amongst Discord servers. It is a high ranking tag of an elite crew and demands respect.
hellafast is pretty damned quick. It's not as fast as stupidfast, but it'll still smoke things that are just "fast". e.g., ASDL is hellafast, compared to a 56K modem.
Man, this rig is hellafast. It beats the hell outta my dual celly rig.