Used to threaten, used to defeat.
Sometimes it grows, sometimes it shrinks.
Used to conquer, used to protect.
It marks your downfall, it marks your success.
The true god of war, the creator of mess.
What is it?
Hint 1:
What do you think when you think of war?
Hint 2(the answer is very very easy once you see this hint):
What do you need to win something?
I guess you mean
power
Used to threaten, used to defeat. $\color{green}{\checkmark}$
If you're powerful, you can threaten others successfully and defeat them.
Sometimes it grows, sometimes it shrinks. $\color{green}{\checkmark}$
Power can grow and shrink (e.g. "political power").
Used to conquer, used to protect. $\color{green}{\checkmark}$
You can use power to conquer foreign and protect your people.
It marks your downfall, it marks your success. $\color{green}{\checkmark}$
Power can be a result of success.
Thank you for this riddle! But from my point of view, the second hint makes it too easy.
