It isn’t just years of inappropriate behaviour that equates to abuse. Being narrow-minded, controlling, one-sidedness, giving someone the silent treatment, expecting someone to mind read and intolerance are also forms of abuse.
I’m not sure how many of us equate some of those forms of abuse above to being part of the abuse scenario, possibly because they have become part of everyday speak. It’s what we know and have come to accept as part of communication. When we treat others unkindly, when we use words that insult, treat others harshly or unjustly that is abuse. Sarcasm is also abuse.
From a lifetime of experience, it doesn’t matter the abuse, no form of abuse is to be tolerated or should be used. We need to watch some of our words too. Words can equate to abuse if those words are used often enough.