If the current trajectory of russian aggression has not yet convinced you, if Georgia’s annexation has not yet convinced you, if Transnistria has not convinced you, if Donetsk, Luhansk, and Kherson have not convinced you (despite pro-russian separatists in the region serving as erstwhile justification for annexation) then I do not know what to tell you.
You are aware that proof doesnt get more solid than repeated, collectively witnessed, action, right? A direct testament from Putin would be less significant than the current record of military intervention.