Frail
Frail, puny, delicate, infirm, sickly, debilitated, ailing, decrepit, tired, exhausted, worn out, feeble, fragile, weakly, sick, shaky, incapacitated, indisposed, enervated, fatigued, spent, and weedy.
Inadequate
Inadequate, feeble, faulty, deficient, substandard, wanting, poor, defective, flawed, imperfect, and lacking.
4. unconvincing
Unconvincing, tenuous, unsatisfactory, poor, thin, unsound, flimsy, hollow, untenable, implausible, slight, inadequate, transparent, feeble, lame, and pathetic.
Dim
Dim, wan, dull, muted, pale, faint, and feeble.
Watery
Watery, dilute, thinned down, adulterated, flavourless, insipid, wishy-washy, diluted, watered down, thin, tasteless, bland, and mild.