La Nina really seems to be a mixed bag, and quite sensitive to the "strength" and positioning of the Nina conditions going into the spring and the impact of other teleconnections as far as its capacity to influence severe weather activity in the central and eastern CONUS.
1974 and 2011 obviously featured the two most prolific tornado outbreaks ever documented, with an unusually great proportion of them being violent, while 2008 was in my memory the most consistently active of the three (although I didn't experience 1974 firsthand as it was before my time) with periodic outbreaks in the Midwest, South, and Plains from January through mid-June.
OTOH, some other very quiet years this century/millennium have also featured some type of La Nina in the spring, such as 2006, 2012 and 2018.