Someone always brings up 655.

Say what you will, the US government at least paid out to the victims (although never officially apologized). While Russia denies all involvement to this day and lawsuits are still ongoing.

Saying Russia did it too and they were much worse about it is not a valid defense of anything.

It wasn’t a defense. Two terrible things happened (let’s assume both accidental). The US admitted Iran-655 was an “accident that resulted in a loss of life” and paid out ~$200k per victim. Russia pretends like MH-17 never happened. Who do you think has more of a moral high ground?

Not defending Russia, just saying the circumstances are a bit different. Iran-655 was downed by a US warship - clear from the outset and no space for argument, while MH-17 was downed by (most probably) Russian separatists with a mobile missiles system, which allows for a lot of deniability, and since they had the chance to deny it they went with it. The US didn't even have that luxury.

Ignoring your initial tone, I see what you're saying, and agree these aren't identical cases. Though it should be emphasized they only payed out to the victims because Iran brought it to the international courts and they wanted to settle. They never, as you said, apologized, or even thought they had any legal obligation to the victims. Feels like your splitting hairs with "Russia denies involvement" as being dramatically different -- both seem like terrible events that neither super power really feels responsible for despite being the ones who put those weapons where they were without legitimacy.