The complete saying should then be:
Πολλοις ο Δαιμων, ου κατ' ευνοιαν φερων,
Μεγαλα διδωσιν ευτυχηματ', αλλ' ινα
Τας συμφορας λαβωσιν εμφανεστερας.
The best I can do with this:
God will bring good fortune to many, not out of good will, but only to make misfortunes appear greater to them.
And for those interested, here is the relevant section in Samson Agonistes:
Yet toward these, thus dignified, thou oft,
Amidst their highth of noon,
Changest thy countenance and thy hand, with no regard
Of highest favours past
From thee on them, or them to thee of service 685
Nor only dost degrade them, or remit
To life obscured, which were a fair dismission,
But throw’st them lower than thou didst exalt them high
Unseemly falls in human eye,
Too grievous for the trespass or omission; 690
Oft leav’st them to the hostile sword
Of heathen and profane, their carcasses
To dogs and fowls a prey, or else captived,
Or to the unjust tribunals, under change of times,
And condemnation of the ungrateful multitude.