The phrase "almost viciously" is correct and usable in written English.
It can be used to describe an action or behavior that is nearly aggressive or cruel, but not quite fully so.
Example: "She smiled almost viciously, as if she took pleasure in his discomfort."
Alternatives: "nearly cruelly" or "almost savagely".
The week before, testifying at the Leveson Inquiry, Brooks, in a Peter Pan collar, had been almost viciously charming.
As Brooks, he is formidable and distant at work, relaxed and authoritative at home, and sardonic and almost viciously funny on his late-night jaunts.
"Transformers: Revenge of the Fallen," directed by the stunningly, almost viciously, untalented Michael Bay, is much closer to the norm of today's conglomerate filmmaking.
Even a privately held company like Bertelsmann finds itself thinking almost viciously about the bottom line because it is hoping to go public one of these days.
There is one concoction, or whatever it should be called, that I was never allowed to eat, and that I dreamed of almost viciously for perhaps seventeen years, until I was about twenty-two and married.
On slavery, Seward was seen as almost viciously anti-slavery.
As I think Nadella quickly realized when he backpedaled from his original statement, this unjust system is not being perpetuated with malicious intent but almost more viciously by well-intentioned people who are unaware of the systematic bias pervasive in the way we do work and allocate rewards.
Never credible as a love story, "Between Love & Goodbye" is viciously, almost hysterically committed to the fracturing and collapse of Marcel and Kyle's love affair.
"He speaks about women viciously and he's just...racist.
The critics have almost entirely panned this movie, viciously so, which is mystifying.
In 2000, two white supremacists beat two Mexican workers living in Farmingville so viciously that they almost died.
