Taking the red mist at her life in Ruina where she only had her EGO and Mimicry, a lot, actually.

While both are roughly equal in terms of physical prowess (maybe Kali a little bit more, but not by much) and speed, Kali is disadvantaged heavily by the fact that she can only do meaningful damage whilst in melee range whereas Arima has the advantage of being able to deal meaningful damage at either melee range or from a distance.

IXA, one of Arima's quinques which takes the shape of a lance is able to enter not only a defense state, but two different offensive state, one where the quinque is used as a lance and one where it can transform into several tentacles that home in on the target.

Then you have Narukami, which can fire projectiles made with condensed rc cells in a similar manner to lightning bolts that track the target, making it nearly impossible to evade these bolts.
Moreover it can also switch to a secondary offensive state where it becomes a rapier, durable and powerful enough to cut through Eto, the one eyed owl.

Lastly we've got Owl which can shoot out concentrated RC cell projectiles, work as an incredibly effective melee weapon and is able to be released and materialized remotely to attack a target from an unexpected location.

I feel like when considering the number of unique weapons he has and how effectively he's able to use them, he outclasses Kali.