Destined to be the most talked about super-villain of the year!
Alexi Shostakov aka Red Guardian aka Ronin (…) might be the most important love interest Natasha has, but he absolutely is the most inconsistently written and confusing. In the world of comics, nothing changes quite like the past. As a perpetual flashback and perpetual seemingly dead guy, Marvel has generally felt free to expand upon his Silver Age origins as a tragic Captain America analogue who fought with a belt buckle in any plot device-y way they see fit. They have also felt free to saddle him with many questionable mustaches.
Honestly, though, belt buckle aside, Shostakov was probably at his best in his very first appearances. He was introduced in the penultimate chapter of the ongoing Silver Age Black Widow plot, and the power of his concept is an obvious one— Soviet Captain America! Considering how many versions of himself Captain America has had to punch over the years, I’d say the broad idea had a ton of sticking power. Indeed, the Red Guardian concept and codename would be reused bunches and bunches of times over the years, as the USSR developed a full compliment of spandex heroes that became known as the Winter Guard.