-Order of Malta. De Jure recognition, no territory or population to speak of. Basically a forgotten joke country left over from a bygone era.
-Trasnistaria. Has population, land, flag, collects taxes. Only recognized by Russia. There's a few Russian backed puppets like this, I won't name them all.
-Taiwan. Already discussed.
-Hong Kong. Mainland Chinese media calls the protestors terrorists. Yet another example of "terrorist" meaning simply "whoever the establishment wants to de-legitimize". If you follow the CCP narrative, the thing they care about isn't Democracy but separatism. "One China" is about not recognizing Taiwan and HK as a matter of ethno-nationalist principal.
-Palestine. Recognized by majority of UN countries. Still not recognized by US, Israel, and associated power block. Why? Because of the stupid belief that recognition will somehow legitimate it.
-ISIS. At their peak they had a sizeable chunk of land, a flag, a capital, civic functions like a court system, an oil industry, handed out passports, were fighting a conventional land war using conventional (not terrorist/guerilla) tactics, had a uniformed army, and the word "state" was right there in the name. But don't you dare call them a state lest someone mistake you for a terrorist sympathizer.
This is why I subscribe to De Facto nationhood instead. A nation is a nation when it satisfies the following properties:
-A plot of land with well defined borders.
-A permanent population on said land.
-A Monopoly on violence over said land.
-An organization capable of credibly making peace, declaring war, and otherwise accepting agreements with other nations.
The last one is tricky as it only specifies the capability not the actualization. For example, if the organization agrees to peace but the individual factions of the army keep fighting then this condition is not satisfied and what you have is a stateless warlord situation. For another example, the ISIS situation clearly had an organization which was capable of agreeing to a surrender or appointing an ambassador, but they never wanted to or were allowed to. The condition is still satisfied even though they never did it.
That's playing a bit fast and loose with the facts there. ISIS conducted public executions, crucifixions, desecration of cultural sites and enslaved people for a labor force. That's textbook asymmetric warfare/terrorism.
To me that just sounds like textbook nationhood. The defining feature of the state is having the monopoly on violence within its borders.
The things ISIS members did to subpopulations people within that territory were almost universally condemned across the world as large-scale serious human abuse, and the territories were obtained through quite recent violence from other nations whose administrative borders had not stopped being recognised internationally.
So I think it was widely regarded that ISIS should not be granted the international respect and autonomy of legal recognition, nor should it keep any power it had of a monopoly on violence within its borders (or any borders).
That's not to say there aren't widely condemned things going on in other countries. But there is a kind of collective, sometimes grudging, but systematised respect for the autonomy of countries as nations, which I think was widely regarded as not something that would be right to grant to ISIS (or take away from the nations that ISIS had taken territory from).
The UN absolutely has provisions in its charter for approved wars. The Korean war was UN approved. A regime that is violent against civilians and outwardly genocidal towards religious minorities like ISIS is exactly the situation UN approved intervention was made for (designed with the Nazi's in mind).
I reject the premise that calling them a state would entail granting them anything.