Currently Garen E only has an 8% crit multiplier on patch 10.23. It seems that Riot took the 10.22 multiplier that was 33% and reduced it by 25% (like they did for AA-crit). . But now on Garen E crit is only 8% multiplier which is useless. Edit: Fixed on 11/13/2020.
Since Garen’s E now scales with attack speed, does lethal rune speed work with it? At level 1, Lethal Speed gives me 40% bonus attack speed, which should be the equivalent of two more spins. No. The number of spins his E makes is based on the bonus attack speed of items and levels, not runes.
The rotation does not trigger hit effects. Black Cleaver is on physical damage, not on hit. And the extra damage the spin deals from your AD can be critical, that’s an exception unique to Garen’s spin.
Judgment also deals 33% more damage to single targets and can also deal critical damage, which is why Crit Master Garen works overall
In particular, his E scales with Attack Speed and Critical Chance. His E gains more spins as he gains more attack speed, and each spin deals bonus critical hit damage.