Mighty No. 9

Hard Mode forces you to only have 2 lives per level at the start and the enemies do more damage and are faster. The extra lives in the level are still available so feel free to pick them up if you feel you need them. (Unlike Ultra Hard Mode)

The REAL ADVANTAGE on Hard mode is that you have all of the powers right at the start!!!! So use battalion's power to blast through the enemies. This makes the run extremely easy. You can just run through the mighty no in what every order you would like.

Utilize the bosses weaknesses to quickly take them out. If you have cleared the game in under an hour on normal this should be no problem.

If you need boss practice utilize the boss rush mode on the normal difficulty. All the bosses are the same except for trinity. I found the boss rush version much more difficult than the Hard mode variation.

For trinity, just used Brand's power to cut at her when she fires the blasts as you have invincibility and then use Cyro's power when she is floating around and attack-able. For her second form I solely used battalion's power for everything. When she pops up in the middle you can quickly destroy the two stacks under her to drop her to the ground. Then you can safely stand on the medium height platform and attack her with battalion without getting hit.
I also had an extra heal tank for this fight but probably didn't need it, I lost only about half of my health.

For the clear hard mode with no restarts, I actually lost all my lives on Shade's level because I was playing like an idiot but if you simply dashboard and then quit the game it did not count against me and I still earned the achievement.

I was able to finish all of hard mode in 1 hour 5 minutes with plenty of deaths and the aforementioned Shade mayhem.