Collocations for weak - adj.

appear, be, feel, look, seem, sound
become, get, go, grow
remain
leave sb, make sb
When the spasm passed, it left him weak and sweating.

extremely, fairly, very, etc.
decidedly, especially, exceptionally, incredibly, particularly
a little, slightly, etc.
comparatively, relatively
fundamentally
curiously
He complained of feeling curiously weak and faint.

surprisingly
dangerously
notoriously
pathetically, pitifully
suddenly
Her legs felt suddenly weak.

inherently
The judge decided the evidence was inherently weak and inconsistent.

economically, financially, mentally, militarily, morally, physically, politically

at
She's rather weak at languages.

from
She was weak from shock.

in
He's weak in English.

on
The essay was rather weak on detail.

with
He was weak with hunger.

weak at the knees
His sudden smile made her go weak at the knees.

Weak is used with these nouns:
acid, argument, arm, attempt, balance sheet, bladder, case, character, chest, chin, coffee, constitution, correlation, cry, currency, current, economy, ego, excuse, force, foundation, government, gravity, grip, heart, hold, knee, leader, leadership, leg, light, link, market, monarchy, performance, personality, point, position, pulse, reception, ruler, showing, signal, smile, solution, spot, state, stem, stomach, stress, sun, sunlight, support, syllable, tea, team, tie, version, voice, vowel, will, wrist