I think Lavrov said the past few days they had weapons that would have very destructive effects if employed. Commentators said they thought he might have referred to some Avantgard missile that has in impact measured in kilotons yet isn't nuclear, 5K lbs warhead or something like that. Like if a long range missile was shot at Moscov the response could be that very destructive non-nuclear missile. I didn't look any of this up now to double check so may be mistaken. Lavrov did mention the word nuclear in the same statement.
Medvedev would say something like what Trump said. But not Putin, or Lavrov. Putin / Lavrov will warn that long-range missiles into Russia could risk a nuclear response from Russia. That's a fair warning. Words like "blown to smithereens" is not the way they express themselves.
Also, bombing a country like Russia with 5kt missiles is different than assassinating a head of state.
But I agree, if Iran did assassinate Trump, they should pay a heavy price. Obviously not everyone in Iran should be killed if that happened.
My problem is, I don't see how Iran would benefit from killing Trump. The Iran story feels to me like a psyop by the Three Letter Agencies (TLA) to set them up as a patsy. The TLA could kill Trump with a drone or missile and blame Iran for it. I am worried Trump is taking his eyes off the TLA because he is scared of them and trying to placate them.
I would have no problem with Trump blowing the TLA to "smithereens"!