How to remove last character put to std::cout?

You may not remove last character.

But you can get the similar effect by overwriting the last character.
For that, you need to move the console cursor backwards by outputting a ‘\b’ (backspace) character like shown below.

#include<iostream>
using namespace std;
int main()
{
    cout<<"Hi";
    cout<<'\b';  //Cursor moves 1 position backwards
    cout<<" ";   //Overwrites letter 'i' with space
}

So the output would be

H