At the time Russia invaded in 2022, the Donbas had seceded from Ukraine. Russia had refused to recognize Donbas independence for years, in accordance with the Minsk II accords, which Russia was trying hard to get implemented.

Russia was negotiating with Ukraine up until December 2021 trying to avoid an escalation of the 7 year old Ukrainian civil war. Ukraine continued to refuse to negotiate.

Instead of negotiating with Russia or implementing Minsk II as Ukraine had agreed to in 2015, Ukraine ramped up shelling of the Donbas and massed troops at the border.

So again, who is the aggressor in the case of Ukraine is, again, subjective.