How to run virtual machine on my nexus device? Are there any virtual machine players such as virtualbox, I can use to run .iso images on Android? If I need the device to be rooted that is fine, but I prefer a portable solution
It really depends on which OS you want to run. Regardless, whenever you want to run a OS meant for computers (x86 architecture) on a mobile device (ARM architecture) a fair amount of time and processing power is needed to convert instructions from one format to other. 

I'm not sure if there is a one stop solution like VMware on Android like that can run both *Nix and Windows OS's. 

You can try the app Windows, Linux, Unix Emulator but I'm not sure how far it will be successful.