Question about metta Does metta mean that we should not ignore people?
Is it possible to forcefully and assertively tell people their wrong doings? What about scolding?
My reservation: If one always remains kind it's likely that people will do whatever they want with you which will result in more problems or not stating one's concerns sufficiently
Human are emotional beings and they usually change if you forcefully and again repeatedly tell them a new way of behaving.

People can also be (or learn to be) bullies -- and unless you are able and willing to be the biggest bully on the block, I suggest that trying to persuade people using "force" is the wrong way to go about it.

To be honest, i.e. to avoid concealing a fact that appears to contradict my thesis, the suttas describe the Buddha has having a "lion's roar" ... and being like a bull among men ...  but,


Perhaps (I'm not sure) that's not relevant to use of force -- for example:


  The Pali Commentaries explain that there are two kinds of lion's roar: that of the Buddha himself and that of his disciples. The former is sounded when the Buddha extols his own attainments or proclaims the potency of the doctrine he has realized; the latter, when accomplished disciples testify to their own achievement of the final goal, the fruit of arahantship.

See also Did the Buddha ever &#39;thunder&#39; during a Fire Sermon?
The Buddha can be trusted to know when what and how is appropriate -- for example:


  In the case of words that the Tathagata knows to be factual, true, beneficial, but unendearing &amp; disagreeable to others, he has a sense of the proper time for saying them.



What about scolding?

I don't know (exactly what "scolding" is), according to the dictionary it's "an angry rebuke or reprimand".

So that seems to get into the question of whether and when anger is appropriate.

There was a topic What is a wrathful Buddha? from Vajrayana where an answer describes that as being like a parent pretending to be angry with their children in order to protect them -- and/or transmuting the energy of anger in a skillful way.

I'm not convinced that everyone is able to be so skillful, though; I think of anger as associated with a loss of skill (like a regression to one's infancy), and generally something to steer clear of. The Dhammapada:


  Na hi verena verani
  sammantidha kudacanam
  averena ca sammanti
  esa dhammo sanantano.
  
  
  Hatred is, indeed, never appeased by hatred in this world. It is appeased only by loving-kindness. This is an ancient law.
  


Another possibility might be that "scolding" implies telling someone something repeatedly or endlessly. I'm not sure that's effective though -- if it were effective, ought you need to repeat it?

Or let us take life threatening situations

I think you might go to the police, or the courts, or use physical force yourself (though this may not have been true everywhere, my personal experience of police leaves me admiring their ability to arrest a person "with overwhelming force" and yet still "without violence" -- like you might restrain a young child near something dangerous).

Or consider a drug addict, for example, asking you to help them to continue their habit.
I think you'd be within your rights to reply, "No, I won't. It's not good for you." (though I'm sympathetic to the fact that people do help addicts).

And I think that when you say "No" like that it doesn't have to be forceful (though it may need to be repeated), nor unkind -- the kinder the better, in my opinion. The kindness may be an even more important part of the message than the "no" (the "no" closing a door but the kindness opening one).



There's also an expression that I thought might be relevant -- i.e., "It's not the size of the dog in the fight, it's the size of the fight in the dog" -- that might help to explain how larger people can be bullied by smaller.

My experience of dogs tells me that's superficially true, e.g. that to deter a cowardly dog attacking a smaller dog, I may to need to be loud and explosive i.e. bark and not remain silent myself: to show it that I have a bigger bark than it does -- that there is (contrary to first appearances) a 'big dog' in me (or "in the fight"), i.e. that I'm the bigger dog.

Among humans, though, it may be more a matter of perseverance than intensity -- unless you can (and are willing to) sustain anger for hours, days, years, you may lose an anger-based competition -- anger is unreliable as a motive (but may fuel your opponent's opposition).

And so, I don't recommend it, I think it's the wrong avenue to pursue or to set off on.