Is there a portable tool (that does not have to be installed) that i can use for file comparision

You can use fc DOS command, but no GUI.

For details:

C:\> help fc

Select all Open in new window

There are quite a few tools, it all depends on your preference of look and feel. Also if you want for free or paying for it

There are some of the portable softwares

TextDiff
WinMerge
DiffMerge
Meld
ExamDiff

Ultra Compare is a top notch text and binary compare program that handles any size of file for comparison. It comes in a Portable version.

https://www.ultraedit.com/downloads/mobility.html

I have WinMerge (lightweight and small files), Beyond Compare (decent) and Ultra Compare (best of the lot).

I agree with comment in ID42071494
The only thing that I would like to add is that it is best to download the main Portable App. This way applications are always up-to-date and you can even install these portable apps in Dropbox etc. and have a main application menu for them.

Here is my "installed" apps