World politics is very complex with lots of nuance, historical context and long-running grudges. It is also highly subjective, in a sense that every country / group of allied countries have their own view of the historical events and try to disseminate those views as wide as possible.

As a result, I've decided to judge countries by the authoritarianism of their regimes and cruelty of their laws. If country's government is treating their own citizens like shit without rights, I do not expect them to treat people on the outside any better, regardless of how they present themselves. Thus, I do not, as an individual human being, want to see these countries / regimes to gain any more power externally.

So far, this approach for me had made most sense.

As a side note, look at the current list of best friends of a corrupt regime in Russia: Iran, North Korea, China, Philippines, Venezuela, up until recently - Turkey. Every dictatorship in the world is on their list of friends. Same with Iran. "When the character of a man is not clear, look at their friends."

Regarding whataboutism and Russia, I want to remind you that my reply to the OP was not about Iranian sanctions, but was about sanctions as a political instrument overall. For me the most prominent case lately were sanctions against Russia, so that's what I used as an example. I'm very familiar with the situation in Russia and even though sanctions indeed antagonized the regime there, it did make them stop and think whether they want to keep escalating. It's hard to imagine what over appropriate response should've been to annexation of the Crimea, downing of the Malaysian Boeing and sending troops and equipment to create essential a civil war in a big region of Ukraine.