The Soviet Union may have earned a reputation of quantity over quality in real life and this is represented in some of the following cards. However, many of these cards express the exact opposite and are some of the highest quality cards in the game that completely define various parts of the game.
Bloody Sickle - One of the few cards that should be run in anything that has the soviets as a main nation or as an ally. On it's own 1 kredit to deal 1 damage is not that amazing but drawing a card along with that makes this insane. Cheap cards that do something to the board while drawing a card are very powerful and sickle is the king of them all. The downside of losing 1 health doesn't matter most of the time due to how you often use this to kill a unit in the early game. If that early unit was to survive it would likely deal way more damage than the 1 health sickle makes you lose. This card just fits into everything from control which loves having cheap removal that does something else to aggro which often uses sickle to kill important targets such as a pesky artillery. Seriously, if you aren't running 4 of these then you aren't playing the Soviet Union right.
Reserves/1271st Rifles - These cards form the core pieces of the soviet token strategy. They are the best way to generate large amounts of light infantry due to how reserves continues to increase. 1K for 2 light infantry is alright but it's not hard to be getting 4+ from each reserves which is a big flood of units from a single card. Reserves is the most common card to be supplying tokens with their seemingly endless amount of light infantry. 1271st Rifles essentially is just the 5th, 6th, and 7th copy of reserves but the 4/6 body is a large threat that can catch the opponenet off guard. Against tokens it is often important to keep their numbers down and people tend to use their bigger removal just to kill a light infantry so slamming down a 4/6 offers a different threat that needs to be dealt with.
Ural Factory - This is a card that requires knowledge of all the units at a specific kredit cost for different nations. Knowing this makes using ural more likely to pull something worthwhile. For example in the soviet union using ural on 5 and 6 cost units will consistently give you a strong unit (at 6k you have stuff like a massive 8/8 infantry, the kv tanks and the only weak unit currently being the 4/3 artillery). 5 and 6 kredits also happen to have very worthwhile units such as the t-34-85 which often are able to attack something, survive, and then have ural used on them which can be very powerful in taking over the board. It is important to note that if there is no unit at a certain cost than ural can't upgrade into it which is another reason it's important to know what units are at what cost.
From the People/The Hammer - A very simple card that many decks can make use of as 3 damage to any unit for 3 kredits is just a good piece of removal. It deals just enough that it will kill most artillery and bombers up until the the late game ones. Even against bigger units due to bloody sickle and some other cheap soviet units it is very possible to kill 5/5s or greater for little cost. Not to mention how it kills essentially all units that have smokescreen making it very useful when the enemy has one of those sneaky units on the field. There isn't much else to say it's a good removal order. The hammer on the other hand is a more powerful effect that is also a bit more narrow. This card on its own will kill practically any ground unit that it hits barring some late game tanks and the higher cost infantry. Due to only costing 3 kredits when you can use this to kill a moderate to expensive unit you can actually generate strong tempo from this removal order. It can be quite back breaking for the opponent when you play a medium sized unit (like the T-34-85 talked about above) and then use hammer to kill the biggest enemy unit.
T-34-85 - For a standard card this has a suprising amount of stuff going on that makes it quite good. A 5/5 tank for 5 kredits would be an unremarkable unit but adding heavy armor 1 changes quite a lot. Suddenly it is able to survive fights becuase most units don't go above 5 attack and the . Add on to that an ability that punishes enemies for using order on it by drawing you a card and you have a surpsingly durable unit that can often survive through a turn to attack. Ural factories also pairs extremely well with this unit due to how often it survives and it being 5 kredits means that ural will consistenly upgrade it into a good unit. This fits well into most Soviet decks either as a strong top end in faster decks or as a solid threat in slower midrange decks.