1 John 2:5 But he who keeps (treasures) His Word [who bears in mind His precepts, who observes His message in its entirety], truly in him has the love of and for God been perfected (completed, reached maturity). By this we may perceive (know, recognize, and be sure) that we are in Him: AMPC

How does this emphatic translation compare to other translations?

But whoso keepeth His Word, in him verily is the love of God perfected: hereby know we that we are in Him. KJ21

but whoever keeps his word, in him truly the love of God is perfected. By this we may know that we are in him: ESV

But if anyone obeys his word, love for God is truly made complete in them. This is how we know we are in him: NIV

I have to admit the AMPC, the Classic Amplified bible, is emphatic in its version of 1 John 2:5. What I see is an expression of depth of relationship. It is almost not enough to say I love God. A simple word cannot fully express the depth of anyone’s love. Here we are not speaking about our love for God but rather His love in us. That abiding love of God.

John 15:10 If ye keep my commandments, ye shall abide in my love; even as I have kept my Father’s commandments, and abide in his love.

God is love, so therefore if you abide in Christ, you abide in His love. Simple enough, yet to say I love is inadequate to express that reality. So how can we fully express perfect love in this imperfect form, our own humanity?

Ephesians 3:19 [That you may really come] to know [practically, through experience for yourselves] the love of Christ, which far surpasses mere knowledge [without experience]; that you may be filled [through all your being] unto all the fullness of God [may have the richest measure of the divine Presence, and become a body wholly filled and flooded with God Himself]! AMPC