Try "Floor" ! A ladder is something to go up and down, a floor is level on the ground.
The antonym of leader is follower.
follower
forceful
Finish is another word for completion starting with the letter F.
The opposite for the word plain starting with letter f is FANCY.
"Führer" with umlaut is the German word for "leader" and Adolf Hitler (starting WWII) was called "Der Führer", in a meaning of the one and only leader of the world - his status was close to a god. Like this he also held all the powers of state.
Floccinaucinihilipilification is the longest word starting with F; it means the act of estimating something as worthless.
The word often is an antonym (opposite) of seldom, and has a silent 't'.
powerful
One word for being late starting with the letter F is forgot.
favor, favorite,
family