I think Shoaib Akhtar's record of 161.3 km/h is pretty hard to beat, but it's difficult to compare bowlers from different eras due to the lack of accurate speed measurements in the past. Jeff Thomson was known for his extreme pace, and many people believe he was the fastest of all time, but there's no official record to back it up. Brett Lee was also incredibly quick, but his top speed was generally measured at around 160 km/h, which is still very fast but slightly slower than Akhtar's record. Personally, I think Thomson might have been the fastest, but without official records, it's impossible to say for sure.