Freeza 2nd Form (after enraged Gohan's assault) or Semi Cell (when he went full power)? Do we even have a reason to believe that any of those power ups has to be greater than 10% or something?
Cell's power up didn't impress anyone whereas Piccolo was alerted by 2nd form Freeza's ki increase, the other ones were too much weak in front of Freeza, so their reactions doesn't value much.