NET

11 Consequently God sends on them a deluding influence so that they will believe what is false.

Darby

11 And for this reason God sends^D8821 to them a working^D8822 of error, that they should believe what is false,

Darby Bible Notes

sends - The present tense is used here as stating the moral fact; it is not present as to time. It refers to the time when the lawless one is revealed, and is in contrast to the present time, which is referred to in v. 7. working - Energeia. a working in the power of anything.

KJV

11 And for this cause God shall send them strong delusion, that they should believe a lie:

Strong's

11 And ^G2532 for this^G5124 cause^G1223 God^G2316 shall send^G3992 them^G846 strong^G1753 delusion^G4106, that^G1519 they^G846 should believe^G4100 a lie^G5579: