First, let's lay out the facts:

• Thu'um are actually words from Dragon language
  
• All Thu'um consists of 3 words.
  
• Thu'um's power comes from the understanding of the words.

Considering the nature of their language (and the dragons themselves), it's baffling how dragons haven't invented a Thu'um for conquering the world or hypnotizing people (or at least killing people by just speaking). Especially considering the purpose of Alduin. Yet they have Thu'um for mundane things like clearing morning fogs and insulting others.

But they do have thu'um to hypnotizing mortals and Dragons, and commanding them to die the very act of killing people lies in your hands as is, not to be confused with my mentioning of commanding people to die, but when one says Yol...you're killing them with the act of speech lol

No, they don't have a Thu'um for hypnotizing people, and when you say "Yol", the target dies because of fire, not because you say something.

Yes, logic says they should be able to create a shout that wins everything for them. That doesn't make it a good reason to actually include it. There's flaws like this in every series, but including that logic is game breaking.

Also worth noting that making a shout requires putting all of your essence into it. It's possible that such shouts would require far too much to create and therefore cannot be created by any currently living thing.