In star wars, General Grievous only ever feared one jedi, and that was Master Yoda, he feared him not because he was strong with the force but because he was small, because if you recall in the attack of the clones, Yoda had to save Anakin and Obi-Wan Kenobi from Count Dooku and he was jumping around everywhere causing Dooku to struggle a bit and since Grievous was a robot he'd have a much harder time trying to defeat him!