Interpreting "last few decades" as within the last 30 years, Timothy McVeigh and Eric Rudolph make the cut.

- 1995 Murrah Federal Building in OK

- 1996 Centennial Olympic Park bombing

Post 2001, Wikipedia has quite a list.

https://en.wikipedia.org/wiki/Right-wing_terrorism#Post-2001

I could see arguing some of these are crimes committed by right-wing groups as opposed to terrorist acts, but others clearly are terrorism.

Yes, there were some yesterday.