Seriously, how can you reach attack over million?

I'm not sure if you mean an overall power of 1M or an APCs Troop combat power or other. However it is easy to keep increasing your attack / power by upgrading the Barracks, adding heroes and unlocking their skills to let you have more troops in each formation and trainnig higher level troops.

Once you reach B22 and have T8 troops and decent heroes you can have 150-200,000 troops in an APC or more. you will have 1M or more combat power in the one march.

A fully upgraded APC with fully unlocked heroes can have over 300,000 troops. At max level you get to T9 troops which will be even stronger.

Getting to these levels can be done with either a lot of time, or spending money.