Ultimately there is only one power and that is love.
We do not have the power to withold love. To love is exercising our freedom. To withold love is exercising our enslavement.
To curse someone is to judge them worthy of a curse. Jesus commands us: 'Pass no judgement and you will not be judged. For as you judge others, so you will yourselves be judged, and whatever measure you deal out to others will be dealt back to you Mt 7:1-2
I therefore suggest that what the Lord is plainly saying is that what we do to others, shall be our OWN reward. if we curse others, then we shall indeed become cursed!
St Paul bids us to ‘pursue gentleness and love’
St Peter orders us 'do not repay wrong with wrong, abuse with abuse, on the contraary, retaliate with blessing for a blessing is the inheritance to which you yourslves have been called 1Pr3:8-9
St James bids us to ‘confess your sins to one another and pray for one another the you shall be healed’ Js 5:16.
To pray for someone is to invoke the Power of God upon them. To curse is to invoke the power of evil. To pray for someone is to receive healing yourself and the forgiveness of your sins. To curse them is to bring judgment without mercy upon yourself and to make yourself ill.
There is in my experience great healing to come from praying for someone who has hurt you and given you every reason not to love them. By persevering with prayer, even if initially, it means praying through gritted teeth, you will be healed and the two of you will be reconciled.