Three BIG suggestions:

1) Killing Wave

2) Propaganda

3) Panharmonicon

Oh! Also comment on my deck now pls because that's kinda how the Advertise forum works...

I feel like you have a few to many single target removal spells. almost all of your instants are removal. I would take some out, and seeing how many 5+ drops you have in the deck, you could probably do with some more ramp spells, being in grixis your best bet is with artifacts, and also Black Market. Also, if you want people discarding cards, Liliana's Caress and Raiders' Wake can add some decent value.

SuperSaiyn7 thanks for the suggestions, an idea I had in mind for lots of my removal spells was replacing them with some more counterspells to make sure no one can do anything I consider threatening. Raider's wake is a card I've considered on and off for a while. Liliana's caress is a card that is surprisingly hard to find in my area, so I've settled with Raiders wake. I just need some more ideas as to what I should add into the deck, like the sort of feel is to cast big splashy spells that mechanically reflect Bolas. So like for example- Increasing Ambition reflects Bolas' ambitions. if you have any ideas then let me know asap.

I'm a little surprised Patient Rebuilding isn't in here. It fits perfectly

Guyvas I honestly have considered it but cannot decide for the life of me which card to replace with it. I'm inclined to think I should take out Notion Thief but I would like some advice on which card you think I should take out.

I love the idea of this deck and Nicol Bolas, the Ravager  ^Flip is my favourite commander to play with! I would strongly suggest you throw in more punishment for discarding, like Bloodchief Ascension or the previously mentioned Liliana's Caress. Creature cards that synergise well here too would be Fell Specter for some more discard punishment and Magus of the Wheel as well as Jace's Archivist to force some bulk discard effects. I have a similar deck to this and have found The Locust God helps out quite a lot when you draw cards to pump out a good wall of chump blockers! Hope this help!

Seeing as how you seem to be going for Bolas flavor perhaps you could consider Hour of Devastation, Crux of Fate, Countersquall, Magmaquake, Neheb, the Eternal, Rakka Mar, and Soul Manipulation.

Other sweet value cards you could consider are Discovery / Dispersal, Rise / Fall, Connive / Concoct, Angrath, the Flame-Chained, Liliana's Specter, Rotting Rats, and Burglar Rat.

I'd for sure run Disallow over Cancel.

AgentJackjohn I was thinking of doing that, however the cards you see here are the cards I currently have so the deck is going to change over the next few months as I find the cards that work. Although disallow was one that managed to slip past my initial vision, so thanks for the idea.