[{quoted}](name=Grym Titan,realm=NA,application-id=3ErqAdtq,discussion-id=GsuRK6R9,comment-id=00080000,timestamp=2017-09-25T16:20:48.011+0000)
In the link you provided, you missed this very important statement. Under the "Movement Speed Caps" section it says:
"The only exception to this is when the slow exceeds 100%, in which case the target ends up with 0 movement speed."
An example of this in play is a level 3 Nunu ult, with Rylais, channeled for at least 2 seconds. http://leagueoflegends.wikia.com/wiki/Nunu
So at 2 seconds of channel, a max level Nunu ult will slow for 85%, plus 20% of that from the Rylais, which equals 102% slow. The calculation works out like:
.85 (ult slow) x .20 (Rylais slow) = .17 (this is the total amount Rylais will add to the ult slow) + .85 (ult) = 1.02 aka 102% slow.
From 2 seconds to a full 3 second channel, this ult will reduce a champion with NO SLOW RESISTANCE OR TENACITY to an MS of 0. With so many combinations and items, its no wonder Nami and Sona are able to do the same thing.
First, don't necro threads. Second, you're just plain wrong on multiple accounts.
Slows no longer stack. And even if they did, it wouldn't be 102%, as slows stacked multiplicatively, not in whatever weird way you were trying to do.