Here are some thoughts and edits:
> Generally, leader
Generally, a leader ...
> People opt them cause
People opt for them because
> Ideas and plans of leader are respected and supported
The ideas and plans of a leader are respected and supported.
One thing to note is that this sentence is in the passive voice (i.e. there is no subject: who respects and supports these leaders?).
Avoid such sentences, particularly when writing for an American audience.
> will not forget forever
will never forget
> I have strong arguments to support my choice.
This sentence is not necessary.
Even if you wanted to use it as a transition sentence, it is not that strong.
> was in war
was at war
> of 20 century
of the 20th century
> In that hard times
Either say: In that hard time OR In those hard times.
Basically this is to align the number (singular / plural) of the pronoun "that" with your noun "hard time".
Anyway, I don't want to go further, in case you don't find this useful and were looking for something else.
If you find it useful, definitely let me know, and I would be happy to help.
I learned writing through a great deal of practice, and so I would love to help others too.
Student or Learner