"Fascism" can be defined in various ways, but historically it took on the character of Nazism in Germany (in it's most extreme form) which saw a banning of trade unions and opposition parties (primarily the German Communist Party, or KPD), significant influence amongst those in the middle-class who saw Nazism as representing a sort of "shopkeepers' socialism," racism against Jews and/or others considered outside of the ethnic German folk community, etc.
In Russia's case, fascism was a very real possibility esp. between the February and October Revolutions in 1917 and/or after a White Russian victory in the Russian Civil War.
IMHO a good way to have Russia go fascist is to have the Bolsheviks falter sometime in 1918, overthrown by domestic counterrevolutionaries with the aid of the British in Petrograd who based their activities within the British Embassy.
Assuming that the Cheka doesn't raid the British Embassy, or that several key British conspirators escape only to continue to plot against the Soviet government, a right-wing military coup is possible which topples the Bolsheviks from power in Petrograd and allows for the Whites to triumph on the battlefield elsewhere in Russia.
So we either get a military junta dominated by White Russian military officers and/or a restored monarchy, both of which the British agent Captain Cromie actively explored in 1918 as viable alternatives to Bolshevism.
The character of this new Russian state would most certainty favor Great Russians over national and/or ethnic minorities.
Land reform will most likely be rolled back considerably, if not entirely, by the new regime, (the Whites only adopted land reform IOTL in 1920-1, when Wrangel was desperate), significantly alienating the peasantry from the triumphant White regime.
With the landed gentry's power in the countryside restored, Moscow, Petrograd, and other major cities could/would very well be put under temporary martial law as the remnants of the revolutionary order are stamped out for good.
Bolshevism would be crushed, its few remaining leaders in exile or imprisoned behind bars or sent to the gulags, which would most certainly be in use by the new regime.
Extreme forms of Great Russian nationalism would be prevalent, taking all of the worst elements of Stalinism and Tsarism and combining them. Russification would commence in the borderland areas of the new Russian state (the Ukraine, the Caucasus, etc.), as the regime would be heavily reliant on the most dominant nationality (i.e. the Russians).
So, worst case scenario is a right-wing military dictatorship and/or a restoration of the monarchy (such as in Turtledove's TL-191 series).
As for Germany going red, for my TL I had a variety of overarching factors lead to a German (communist) revolution; The Soviet-Polish War ends in a victory for the Soviets, and thus Poland is carved up between Wiemar Germany and the Soviets.
This puts the Red Army in a position to exploit unrest in Germany despite the somewhat cordial relations between the Soviets and Wiemar Germans at the time. Keep in mind that the Soviets were still itching for revolution in one or more European countries, something which the Third International was to facilitate through the organization of communist parties on an international basis.
Come 1923, Germany is facing hyper-inflation, its economy in ruins, and to add salt to the wound the French enter the Ruhr. Resistance to foreign occupation is heavy along the border, while a general strike threatens to break out in Germany.
In my TL, the KPD (German Communist Party) takes advantage of the situation to hastily seize power in numerous cities and towns throughout Germany. The Red Army enters on the behalf of the KPD from Soviet Poland, further intensifying the German Civil War. IOTL it was hoped that a Red Army entry into Germany would set the powder keg ablaze, so to speak.
There, a communist Germany.