The phrase "a complete afterthought" is correct and usable in written English.
It can be used to describe something that was not considered or planned in advance, often added later without much importance.
Example: "The additional feature was really just a complete afterthought, added at the last minute without much consideration."
Alternatives: "an afterthought" or "a mere afterthought".
Dessert, however, is a complete afterthought, stretching little further than ice cream and fruit salad or panna cotta, the latter being much like the chips.
Deposits are a complete afterthought for Goldman, and still remain a minor component of Morgan Stanley's business despite plans to add Smith Barney deposits to its brokerage and closer ties to a Japanese commercial bank.
In that sense, Somewhere on a Beach shares the same DNA as Cole Swindell's recent hit Ain't Worth the Whiskey, in which the singer repeatedly insists that he isn't getting smashed over his ex-girlfriend because she's such a complete afterthought.
And I hope it spurs the development of more content and tools that are presented to us as if images aren't a complete afterthought.
The game's multiplayer mode was added late in the development process; Martin Hollis described it as "a complete afterthought".
I get that they were treated as comic relief, but, as part of the story, they're a complete afterthought.
It is both a temple and a complete exposition of doctrine, designed as a whole, and completed as it was designed, with only one major afterthought.
According to Fleming's biographer, Andrew Lycett, after the novel was completed, "almost as an afterthought, [Fleming] appended four extra chapters, recording what happens on the Queen Elizabeth"; and allowing the question of marriage to arise, because Bond falls in love with Case, the first time he has done so since Vesper Lynd in Casino Royale.
It felt a bit like an afterthought.
Battery drain should be a priority, not an afterthought".
She was at most a decoy, almost an afterthought. .
