I guess the “new database” isn’t counting any of the deaths in 2020 at the hands of leftists who, I am sure, would characterize themselves as “anti-fascists”. Regardless, the FBI characterizes 49% of the killings as not right wing. Apparently they do not share the Guardian’s point of view.
The “329” killings by “white supremacists and other rightwing extremists” is not detailed in the article itself. But over half of them were the Oklahoma City bombing by one man, Timothy McVeigh. McVeigh was a self-styled “anti-fascist”, “animal rights” meth-head, paranoid who cannot really be described as political in any meaningful sense.
As to the other 49% of “right wing extremists” who and what were they? Some, we know, were “incel” whose main thing is being anti-female, and whose exact politics, if any, aren’t part of their self-identification.
It really is a shame that so much anymore is political propaganda. It could be interesting or useful to know who the political killers really are. But in today’s climate it’s probably not possible to know very much because so many things are re-molded to serve as anti-Trump propaganda.