So, the question is: Has there been any war that the Russia has ignited
since WWII ever in its history, that has NOT been self-excused as a support of a newly-created marionette "Republic"?
Well, any point of Russian history is acceptable, right? We have a lot of interesting candidates. Let's see some of them:
The Russo-Swedish War of 1590–1595 between the Tsardom of Russia and Sweden seems to fit what you want. If I can believe wikipedia, this war was instigated by the Russian Regent Boris Godunov hoping to recover the Duchy of Estonia, which was taken from Russia in the previous Livonian War - so there was not an excuse of supporting a "marionette Republic" (or Kingdom). According to the wiki:
As soon as the Truce of Plussa expired early in 1590, a large Russian army led by Godunov and his sickly brother-in-law, Fyodor I of Russia, marched from Moscow towards Novgorod. On 18 January they crossed the Narva River and laid siege to the Swedish castle of Narva (...).
Maybe someone could say this war was not ignited by Russia, since there was previous wars against Sweden, including the one where Russia lost the Duchy of Estonia.
Then there was the Russo-Persian War of 1722–1723:
The formal pretext was the grave damage inflicted to the many Russian merchants who inhabited the Safavid Iranian city of Shamakhi. In 1721, rebellious Lezgins, from within the declining Safavid Empire, had sacked and looted the city, killing many of its inhabitants including several Russian merchants.
However, according to wiki, "the ultimate cause of the war was Russia's desire to expand to the southeast and the temporary weakness of Iran", i.e., the war was ignited by Russia, and the formal "excuse" was the damage suffered by Russian merchants in Persia, not the support of, let's say, a "People's Emirate".
About recent wars: most Russian wars after WWII seems to, formally, be either in support of new communist or post-soviet states, about crushing some kind of rebellion (so formally ignited by the rebellion itself; for example, Caucasus Insurgency, Hungary Revolution or the invasion of Czechoslovakia), or involved mainly other countries which were the ones who formally ignited the war (as North Vietnam, Egypt in the War of Attrition, or the wars between Ethiopia and Eritrea). Wars after 1917 seems to follow the same pattern, including wars which formed the Soviet Union and its constituents.
Some possible exceptions to this includes:
- The Sino-Soviet Conflict in 1929, fought for the administration of the Chinese Eastern Railway (CER), which was a joint management between the non-communist Republic of China and USSR. The first country to attack was the USSR. However, since the war started after China arrested the General Manager and other Soviet citizens of the CER, a move in response to maneuvers by the Soviet to retain most control of the company by, for example, hiring more Soviet workers and officers, it's pretty hard to state who "ignited" it.
- Soviet invasion of the Baltic States: there was no existing "People's Republic" in Estonia, Latvia or Lithuania (unlike Finland, although the communist puppet state in Finland was created soon after the start of Winter War). The Molotov-Ribbentrop Pact, which forced them to sign "mutual assistance treaties" and give freedom to Soviet forces in their territory. Then the Orzel Incident happened, when a Polish submarine escaped from Estonian capital, Tallinn, to UK, so the Soviets questioned Estonia's neutrality and forced them to allow the establishment of military bases by the communist countries. In the end, the three countries were accused of "conspiracy against the Soviet Union", and this was the pretext for the invasion - no existing "People's Republic", and the whole situation is such that it's hard to argue that this war was not "ignited" by USSR. However, soon after the invasion, of course new communist governments formed in the three countries, so this situation may not count.
- Zhenbao Island Incident between USSR and Maoist China in 1969, one of a series of border incidents between the two countries after the Sino-Soviet Split, but it was PRC who started to attack in this one.
- Border conflicts between Imperial Japan and Soviet Union in the 30s, where both sides claims that the other one was blame of border violations. There was no newly-created People's Republic there, although communist Mongolia participated of the battles. However, the excuse here is border defense, and it's hard to argue who "ignited" this conflict.