The phrase "almost too weak" is correct and usable in written English.
It can be used to describe something that is nearly insufficient or lacking in strength or effectiveness.
Example: "The argument presented was almost too weak to convince the jury of his innocence."
Alternatives: "nearly insufficient" or "practically feeble."
When Vivian is almost too weak to talk, the aged E. M. Ashford arrives.
This Brutus is so openly self-questioning that he's almost too weak an opening act for Mark Antony (the strapping, handsome Ray Fearon) at Caesar's funeral orations.
In practice, this means doing the dirty work for Semyon (Armin Mueller-Stahl), a restaurateur with fingers in many unpalatable pies, and for Semyon's son Kirill (Vincent Cassel), a cringer almost too weak for wickedness.
When you finally reach the top, you're almost too weak to stake in a flag.
Older villagers considered the milk 'dirty' and 'useless.' As a new mother, Ms. Sangha wasn't given any food to eat for three days, just turmeric water as part of a purification ritual that left her almost too weak to begin breastfeeding.
But the president is almost certainly too weak for such a rash plan to succeed.
The cut was "almost certainly too weak to do the job," Paul Krugman, the _Times' economics columnist, agreed.
But in each case the measures taken were half-hearted -- moves in the right direction, but almost certainly too weak to do the job.
Voices calling for the kind of sweeping, liberal reforms that might have pulled Arab countries into line with the rest of the world almost always proved too weak.
The capsule bumped to earth on the Kazakh steppes and tipped on its side, the astronauts said, leaving the crew hanging almost as if from the ceiling, too weak to extricate themselves for close to an hour.
"I'm too weak to walk and almost too tired to care," she added, her voice dropping to a whisper.
