Personally, I think 2016 had fewer violent tornadoes than 2018. Chapman was obviously F5 and Katie was violent. Woodburn, Indiana has a case.
2018 had 5 violent candidates: Camp Crook, Tescott, Laramie, Douglas, and Alonsa
2005 was the least violent year in living memory imo. Earlington, Kentucky has the only argument for violent status. And that was in mid November, not spring! Another similar year was 2000. The 3 violent tornadoes were in July, September, and December.
In this century there have actually been 4 years with no violent-rated tornadoes in spring: 2000, 2005, 2018, and 2021. However, Tescott 2018 was May 1