Nick Fury, the man with the plan. Nick has seen and thrown down with some of the worst and deadliest. An ever watchful eye, most don’t realize it but he is the reason the avengers can do what they do and is also a very big reason earth is still safe.
So with all that in mind, you’ll have to wonder….what if Fury was actually a bad guy, say a spy for Hydra or even worse a mastermind plotting to bring the world to it’s Knees, would we stand a chance?
Now note for the sake of this write up we will be sticking to the MCU, the comics are too broad and convoluted for me to attempt something like this, not that the MCU isn’t big but quite frankly I’d take my chances with the MCU instead!

Nick was instrumental in starving of the Kree invasion, he help Tony on a few occasions during his adventures as Iron man and his crowing achievement might be the most important piece of history in the entire MCU. He brought the Avengers together.

It is things like that that make you glad he’s on our side! So now let’s take it that for some reason Fury wanted to destroy or take over the world…what would happen? I think the events of Captain Marvel would remain the same.
Fury would be hard-pressed to conquer earth if it were a kree colony, so he would most definitely do all he could to prevent that from happening. Things would begin to divert as we get closer to Loki’s invasion especially during the events of the various Iron-man movies.
Upon realizing the threats out there and rightfully concluding earth was in no position to defend itself, he would start utilizing his resources at Shield to consolidate power, discussing and meeting with individuals with similar ambitions.

For one thing I don’t think Cap would survive after been found. Fury would most likely have him assassinated while he’s still comatose. Cap would be too big a threat for his plans of global domination, one he would most certainly want to nip in the bud, and given the resources at his disposal, he would most certainly do so.
He would also be communicating with the likes of Obadiah Stane much like he was with Tony prior to the formation of the Avengers. I think Fury would advise Stane to delay his plans until a better time, preventing his demise and thus giving Fury access to Stark’s tech.

After the events of the hulk he would keep an eye on the Vault and the abomination and after the events of Thor he would also look into Asgardian magic, investing in finding out how the Destroyer operated and seeing how he could secure it.
In essence by the events of Loki’s invasion, he would have enough to take on the Chitauri invasion, but especially with Cap gone it is highly unlikely they would be able to stop Loki’s invasion, A nation like Wakanda might hold out a bit longer but eventually succumb.

Fury would of course still seek to oust Loki, probably undermining the trickster god’s rule from the shadows until the likes of Odin or the Ancient one ultimately remove him, but essentially the avengers would never exist leaving the earth defenseless against Thanos who would eventually secure all the Infinity Stones. Half of all life would be wiped out including Fury, leaving the universe a hot mess!
Now of course all of this was just speculation, things could have gone differently but still you can’t help but be glad Fury is one of the good guys!