I have a hard time choosing between Foster, Butler, BBK, and peak Azeem. I might lean Foster. He definitely had the most productive career. BBK's 2018 season was the best any had, and it's hard to argue with first team AA by four publications, including the AP.
Butler was not a better college player than BBK and it isn’t really close. He has better size. That’s it. BBK had better instincts, was faster, and was more of a playmaker.
Foster was the only reason the 2010 defense was decent at times. It would have been just like 2011 if he were not on the team. He played a long time in the NFL despite being overweight and slow for most of his career.