Well, obviously Marxism-Leninism would have little importance, and Revolutionary Leftism at large would be... discredited, at least in Europe. This certainly does not mean that Marxism in general becomes marginal (Marx was fairly influential in the far-Left by then, and he was a powrful thinker whose ideas would still be discussed). But the Leninist "Vanguardist" approach would lose a lot of credit. There would be no hegemony of Bolshevik-derived discourse in the Left. On one hand, that would go into support for various forms of Social Democracy on one side, and various strands of Anarchism/Syndacalism on the other. The Interwar KPD or its equivalent would either have a different ideological trajectory, or a much diminished importance, for example. Likewise, the Communist/Socialist split in Italy and France would take very different forms and likely be delayed (though in both countries, as in Germany, the underlying differences had already made Socialist unity a polite fiction at best, so I think some sort of split is difficult to avoid).
The key point is that, here, the party of the organized Socialist workers trying to seize the control of the state apparatus is militarily defeated in the attempt (somehow; I suspect that a White victory is not very easy to do) showing that this strategy is unlikely to ever work. Thus, Revolutionary minded groups would have to think of different strategies (non-Vanguardist ones, probably) while more conciliatory ones would try and play the rules of bourgeois Democracy whenever possible, aiming at expanding their chances of working within that framework, which was the main strategy of British Labour and the majority fraction of French and German Socialists even before WWI (when the choice to support the war put it under major stress).
One problem here is that post-war, any sort of even remotely working Socialist International is hard pressed: how does Worker Internationalism function even as a polite fiction, after the French and German elected representatives voted for nation over class, i.e., accepting that workers have a national fatherland after all? And the committed Internationalists have not the Soviet Union as an example (however flawed) to look at.
Of course, the specifics of how the Bolsheviks lose are important. A longer, if unstable, Socialist unity might , even if I don't see a clear path for that, lead to successful "revolutionary" regimes elsewhere (Germany, Italy, perhaps Hungary are the least unlikely candidates, but all are very long shots).