How do I beat Ivy on New Game Plus?

Every time you climb up a level, run to a thug on the far left or right side and start attacking while he's getting out of the cocoon. If you do it right, you can knock one down and ground takedown them before the rest of the goons can run to you.

For the first few floors, be patient. There is no time limit for taking them out, so focus on striking and evading. You should be using the evade function more than the counter function by now, as it sets you up for another (hopefully) critical strike which will do more damage than a counter.

The final floor is very difficult, as Ivy's spores can be hard to dodge and do a lot of damage. Stay as close to the edge of the platform as possible, so you can have maximum reaction time to the spores and you can hopefully knock some thugs off of the platform. Spam evade once you see her flowers charging up, and you should be okay.