Are you implying that Russians invaded Ukraine to kill that soldier? If not than you have to agree that that was a sad incident. It's not like there was a battle.
And then you should also ask yourself how can you seriously equate a total bombardment of a country (or full scale military invasion) with one incident of death.
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Russia had a legal right to have any troops at its Crimean base. Up to 25k. Not just Black Sea fleet ones.