That's not how the political spectrum works. For one, plenty of political features don't belong on any sensible left-right spectrum (authoritarianism? electoral laws? judicial system?) which makes it obvious that there is no reason why a far-right government and a far-left government cannot have things in common.
In that case, if the left-right spectrum ignores huge parts of political structures, can it really be called a political spectrum?
The left-right spectrum is just a model. Models make concepts easier to understand but inevitably leave out some important aspects.
Now you're getting it!
By that reductive definition, however, fascism is the archetypal far-right ideology.
But then the term “far-right” is then mostly useless for actually assessing a political ideology.
There are different ways of being far-right. Fascism and libertarianism could both be considered far-right even though they are polar opposites on many issues. The former is far-right based on cultural/identity issues while the latter is far-right on taxation/spending issues.