One of my favorite hobby memories is sharing time with a gent who wanted a scenario where I was completely subservient to him and treated him like a king throughout. He was very dominant and assertive. And from the moment he walked through the door, he instructed me to take of his jacket and tie, and then his shoes and socks, and proceed to kiss his feet. And work my way up, while messaging and kissing his feet, calves, and thighs.
After some extended sensuous oral action, he then switched gears and got a little more aggressive. Which included pulling my hair, slapping my face, and spanking me. And eventually some intense anal action. There was more and more trust built up each time we saw each other. And what was most important was that he respected my boundaries and limits. For example, I love being spanked on my ass really, really hard, and luckily, I don't bruise easily. Whereas, with face slapping, I only like light contact and pain.
There is no general answer to the question: "how aggressive is too aggressive?" Chemistry is important. And communication and consent are crucial.
I happen to enjoy some sexual aggression but there are levels to it most definitely.
Even though I dabble into light BDSM, I'm more into the sensual side of the lifestyle, not pain.
With the right partner, I believe it's more about the attraction and chemistry ... The rest will follow...
You should def ask/pm provider you have in mind as we all have different comfort levels. It also matters on who is being the dom and the sub. It never hurts to ask/discuss what kind of session you are wanting.