Shot in the dark, but MLK combined with JFK? MLK likely wouldn't become President or anything but I don't think it's outside the realm of possibility for him to, say, form a single-issue Civil Rights Party in the event that JFK isn't killed and the CRA is killed in Congress? Of course, I'm not an expert on the subject, so feel free to correct me.
Going back to what I'm a bit more knowledgeable in, Yuri Andropov. He was basically the de facto paramount leader of the USSR since 1975, and if he can serve and live for a bit longer --- say, 1982-1990 instead of 1982-1984 --- then his domestic policies focused on crushing truancy in civilian industries and local autonomy for certain industries would help increase Soviet production (OTL they did by about 4%), while his anti-corruption initiatives likely wouldn't go far enough to eliminate corruption but it would deal some significant blows (OTL he basically reversed Brezhnev's tacit acceptance of corruption and fear of conflict and self-criticism, dismissing many government officials and even starting high-profile criminal cases against high-ranking members).
This, of course, is going to be coupled with Andropov's incredibly authoritarian social policies that would make Stalin blush. He hated anti-socialist dissent (despite promoting reformers like Gorbachev) and hid the fact that the Soviets shot down KAL 007 on accident, framing it as an act against western provocation. He also raised the Soviet military budget a ton which wasn't really helping anybody and floundered quite a bit on foreign policy.
Ultimately, I feel like Andropov living a few years longer might let the USSR trudge on for maybe a decade or two --- more internally authoritarian, but ironically a bit more liberal in foreign policy. He opposed sending troops into Poland during Solidarity's debut around 1980 and opposed the war in Afghanistan, but at the same time he'd probably ramp up military spending to nations like Syria, Libya, and Cuba like he did OTL. This isn't going to bode well with Reagan, another hawk, in the White House. Andropov wanted to avoid open war but during his tenure relations with the West plummeted.
Lenin doesn't get shot by Fanny Kaplan and lives longer maybe Stalin is avoided.
I doubt it. Stalin was well-liked by much of the party and was ideologically orthodox; by the end of his life Lenin even began agreeing with Stalin's positions on Socialism in One Country and the NEP, and Stalin became pretty famous for his synthesis of Marxism-Leninism and astute politicking. Regardless, Lenin's family had a history of serious heart problems and his father died relatively young. I doubt simply not being shot would save his life.
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