Which is a easiest branch in engineering
There is no such thing as easy or hard it all depends on your interest in a particular field.
If you have keen interest in coding you might feel computer science as an easy engineering branch while mechanical engineer might be difficult for you.
Similarly if you have interests in machines and instruments, instrumentation engineering would be easier for you while you would feel computer science as a hard nut to crack.
And for any branch it is very important to work hard with utmost dedication to excel in that particular field
Hope that helps