You made a good impression on me from the very beginning.
'Impressione' = im-pres-SIO-ne. 'Dall'inizio' = dal-l'i-NI-zio.
Use this to express that your positive perception of someone began immediately upon meeting. It is a meaningful compliment that acknowledges the quality of a first impression. It is suitable for both casual and slightly more formal new friendships.
'Fare buona impressione' (to make a good impression) is a common Italian phrase. 'Sin dall'inizio' = 'since the beginning / from the very start'. 'Sin' is a more emphatic version of 'da' and is used before 'dall'' for rhythmic reasons.
Ho capito subito che eri una persona speciale.
I understood immediately that you were a special person.
Even more personal compliment about their character
La tua prima impressione è stata ottima.
Your first impression was excellent.
More formal phrasing of the same idea
Ti ho notato/a subito quando sei entrato/a.
I noticed you immediately when you came in.
Physical noticing — can sound romantic in some contexts, so use carefully
Italians pay significant attention to first impressions, reflected in the concept of 'fare bella figura' — presenting yourself well. At the same time, they are attuned to authentic character beneath the surface and will quickly sense if someone's good impression is genuine or performed. Genuine warmth is always preferred.