The phrase "almost thoroughly" is correct and usable in written English.
It can be used to describe a situation where something is nearly complete or comprehensive, but not entirely so.
Example: "The report was almost thoroughly reviewed, but a few sections still needed attention."
Alternatives: "nearly complete" or "mostly thorough."
Retracing a 1935 trip through Sierra Leone and Liberia made by Graham Greene on behalf of a British antislavery organization, Butcher and a young companion encounter a wasteland almost thoroughly destroyed by years of conflict.
As the drama moves to its dark conclusion, the tension that initially filled the room — the ego conflicts of the writers and the curiosity about the identity of the 27th man — has almost thoroughly dissipated.
After the whole treatment processes, organic matter in POME expressed by BOD and COD was removed almost thoroughly.
Within arthropods, embryonic patterning has been most thoroughly studied in the fruit fly Drosophila melanogaster, in which all segments form almost simultaneously at the syncytial blastoderm stage.
And the space felt almost as thoroughly transformed.
Instead, politicians decided to order something that was almost impossible, thoroughly impractical and utterly elitist.
And Mr. Kloves has immersed himself so deeply in the world of Harry Potter that by the time J. K. Rowling's seventh and final volume, "Harry Potter and the Deathly Hallows," came out in 2007, he said, he knew the characters almost as thoroughly as she did herself.
"The atomic bomb -- America's top secret, remains a secret," an announcer intoned, unaware, as was Hoover, that while the secret had been successfully hidden from Germany and Japan it had been hijacked for the Soviet Union, whose agents had insinuated themselves into the American government almost as thoroughly as the F.B.I. had infiltrated the American Communist Party.
Their wet meeting at the truck, she wiping, he noticing, she noticing his noticing; also, accidental brushings of arms, a loose button and a Perseid shower of casually exploratory yet charged remarks: these ensnare the reader almost as thoroughly as the couple.
MO can be almost degraded thoroughly after 90 min treatment by Zn-In-3, 70 min by Zn-In-5, and only 60 min by Zn-In-4 composite photocatalyst.
(Okay - almost as thoroughly).
