Russia was a paper bear (tiger) prior to WWI and by no means on course to surpass Germany as the dominant power in Europe. There was a perception that Russia was very powerful, thanks to its size, militarily and politically, but it quickly demonstrated its major failings early on in the war. The Romanov dynasty and regime were impressively incompetent, even when compared to the other incompetent leaders of Germany, France, and the UK. Russia's only strength was its size and population. Since it had not industrialized on a large scale, it couldn't compete economically with the other three great powers.
As for the losses they took in WWI and WWII, a large proportion of those losses are self-inflicted whether deliberate or accidental. Russia got its ass handed to it in WWI because of the downright terrible state of the military and leadership. The same goes for the first few years of WWII, largely as a result of Stalin killing or otherwise eliminating all of the military leadership. The nature of the war on the Eastern Front was very different from that on the West. The Germans and Russians treated each other like animals. Stalin treated his own military and population as completely expendable. The barbarity by both sides in the East was shocking. Fortunately for the Soviets, they were on the winning side against the Nazis so their atrocities don't get as much attention. They were doing literally the same thing that Germany was prior to Barbarossa.
Whether or not Russia was going to surpass Germany is irrelevant to the perception that Germany had of Russia. Russia was a massive country with a massive population that was on the verge of industrializing. The perception in Germany was that Russia was sooner or later going to unseat them as the dominant continental power. "Europe's Last Summer" is the book that posits this thesis. That WW1 was two wars, the Serbian/AH war and the German/Russian war. Germany didn't want to avoid war, it WANTED the war. Every other actor was hoping to avoid it. It is, imo the best argument regarding the start of WW1, it is well supported and well received. In a perverse way, Germany was also itching to implement Moltke the Younger's plan which is colloquially know as the Schlieffen Plan.
I don't really need a lecture on the Eastern Front, I'm somewhat versed in it. I will however correct you. The losses the Soviets took in the first few years of the war, largely occurred in the first 3 to 4 months of the war. Somewhere in the neighborhood of 5 million men were irrevocably lost. Contrary to popular belief, it wasn't due to the purges (though that contributed). It was due to the fact that the USSR was significantly outnumbered on the front, and they were taken almost completely by surprise.
You're right. The Eastern Front was unlike the Western Front, so to apply the same expectations on morality and conduct is strange. From the very beginning it was clear to the Soviets that they were facing an existential war. The brutality was fundamental. Stalin was absolutely a monster, and he absolutely did what was necessary to win the war. The manner that Stalin fought the war, was ice cold and completely calculated. I would also appreciate you to provide exact instances in which Stalin needlessly threw away the lives of his soldiers and population during WW2. I think you will find you won't be able to. From almost day one, the Soviet methodology was to ruthlessly counter attack the Germans at every and any opportunity. In the process they took horrific losses, but they also inflicted horrific losses. Germany was done by December 1941. The war was over, Germany was already bleeding white. For an example Großdeutschland, which at the time was a Motorized Rifle Regiment, which began the invasion with an actual strength of 6,000 men, was disbanded and reformed as a single under-strength rifle battalion by the end of the Soviet Winter counter offensives in December. That is just a couple hundred men, from 6,000.
The USSR fought in a manner that it knew it could fight in and win the war. They fought in an attrition manner because they had to. Germany took losses it couldn't afford. The USSR took losses it could afford. By January 1942, Germany knew it had lost the war. Paraphrasing a high ranking German staff officer (I forget who specifically), he said basically "We've lost the ability to win the war by military means".
Shifting the blame of Russia/USSR's military losses on itself, is akin to blaming a woman who was raped for looking alluring. Russia did not initiate either war, and the defense she put up was the best it could do at those times. Military losses in defense of your country when you are the defender are never your fault. I shudder to think what would have happened in Eastern Europe without an individual like Stalin running things. Imagine for a moment if Stalin was no running the USSR, someone perhaps more rational. Imagine if the Soviet Union surrendered after it lost 5 million men in 3-4 months. Imagine the size and scope of the holocaust. Imagine the political landscape of Europe. No USSR in the war = No allied landings anywhere = no allied liberation of Western Europe. Without the Soviet Union staying in the war after getting so completely obliterated in the opening months, there is no Allied invasion anywhere in Europe. The death toll in Labour Camps/Death Camps wouldn't have been a little over 10 million, it would have been who knows how high it would have been.
Returning to Ukraine, your point about "Fortunately, they were on the winning side" is both poignant and ironic. The narrative shifted towards the USSR as soon as they were deemed to be the enemy. During the war, the opinion of Stalin and the USSR was glowing, both Churchill and Roosevelt had what you could call "broners" for him. The darkside of Stalin and the USSR was glossed over, they were carrying us to victory in Europe afterall. As soon as they were the enemy, we got the complete opposite. The darkside was emphasized at the expense of everything else. The fact that the USSR defeated Germany nearly single handed was ignored. The roll of the USSR in winning the war was downplayed completely to the extent that many people still to this day believe that the UK and the US were the single biggest reason for Germany's defeat. That the Battle of Britain was the defining moment, and that without Lend Lease and Strategic Bombing the USSR surely would have fallen!
In Ukraine it is more of the same, Russia is now "bad", and we don't get the whole story. It is completely ignored in Western media that the coup which overthrew the previous government was completely illegal. It violated Ukraine's own constitution. Parliament threw him out "officially" but it did so without actually abiding by their own constitution. It would be nice to have some balance in the discussion. It would be nice for major media outlets to point out that the situation in Ukraine is not as simple as "tyrant overthrown and Russia is invading!" It is far more complicated than that. If Western Ukraine has the right to apparently illegally through out a President, then Eastern Ukraine has the right to do the same thing. If the West can fund money and weapons to the West, then Russia can to the East. Both sides are doing EXACTLY the same thing, but we hide our own shenanigans.