The phrase "an often vicious" is correct and usable in written English.
It can be used to describe something that frequently exhibits cruelty or malice.
Example: "The debate turned into an often vicious exchange of insults that left both sides feeling hurt."
Alternatives: "a frequently brutal" or "a commonly harsh".
There were reminders of sacrifices made to win fundamental rights from an often vicious racist regime.
The film has outraged some of Jackson's fans, who have waged an often vicious social media campaign against his accusers.
Benedict Brogan on his blog says Benn led an "often vicious struggle to change the country for the worse".
The debate during the campaign reflected the national debate over spending and closed with an often vicious round of robo-calls, fliers and accusations.
I also want to pay tribute to you for the great dignity you have shown in the face of an often vicious attack from certain section of the press.
But if Le Canard is all about scoops and unreported secrets, Charlie is both cruder and crueller - deploying a mix of cartoons and an often vicious polemical wit.
He is a wily, often vicious politician who knows how to manipulate individual ambition and nationalistic ardour.
It was, for many, a moving reminder of how hard freedom had to be fought for, with terrible sacrifices, against a racist, often vicious regime.
In 1991, Kiselyov made a name for himself by refusing to go on the air and broadcast the Kremlin line about an attack on the Baltic independence movements, but now he is an enthusiastic, and often vicious, voice in defense of the state.
In 12 years as a grand prix driver the 37-year-old Australian has always been the most warm and human of competitors in a cold and often vicious business, so it was hardly surprising that last weekend, after the Singapore Grand Prix, he hitched a lift back to the pits on the Ferrari of his friend, Fernando Alonso, or that he has since received a 10-place grid punishment at the next race in Korea.
Online harassment has become a pervasive and often vicious problem with real-life repercussions.
