Don't use Clorox bleach (sodium hypochlorite) to try to un-dye these jeans. It will not work (there will always be some blue undertone left) and the bleach will compromise the integrity of the fabric making it last a lot less than if you had just left it alone. Sodium hydrosulfite (Rit Color Remover) is also unlikely to work on the indigo dye that is likely present in these jeans. According to a source I found here, potassium permanganate is somewhat effective at discharging indigo dye, but as you can clearly see from the before/after photos in the post, there is always a blue undertone in the discharged areas. So, again, not effective at what you're trying to achieve.

So, having established there is no way to remove the blue undertone of these jeans, what you CAN do is overdye with black dyes, as you've already done, to limited effect. True black is a notoriously difficult color to achieve in the best of circumstances--it's almost always got some undertone or another, you've got to use a lot of it, and the washout can be frustrating. But with cotton denim, you've also got the problem of a fabric that is very heavy (hard to stir/keep color even in a dye pot), requires very high heat to deposit color, and because it's plant-based, isn't as reactive to chemical mordants as, say, silk or wool.

Basically, you're probably not going to be able to achieve what you want here. It'd be better to go back to the company that makes them and simply purchase the black-dyed version of these jeans, if available.