I wouldn't change you for anything in the world.
non ti cam-bie-REI per NIEN-te al MON-do — stress on 'rei', 'nien-', 'mon-'. 'Cambierei' is conditional: cam-bie-REI.
Total acceptance — saying you would not change a single thing about them. The ultimate statement of unconditional love.
'Non ti cambierei' = I would not change you (conditional of 'cambiare' — second person). 'Per niente al mondo' = for nothing in the world — an absolute, emphatic expression of unconditional commitment. The conditional adds elegance.
Sei perfetto/a così come sei.
You're perfect just as you are.
Direct statement of sufficiency — no modification needed or desired
Amo tutto di te, anche quello che non ami di te stesso/a.
I love everything about you, even what you don't love about yourself.
Includes self-disliked aspects — total acceptance beyond self-acceptance
Non cambiarti — sei già abbastanza.
Don't change — you are already enough.
Imperative of non-change — protection of who they already are
The idea that someone's flaws and struggles are part of who they are — and loved for that reason — reflects a mature Italian view of love that goes beyond romance into genuine partnership. 'Ti hanno reso chi sei' (they made you who you are) shows respect for the whole life story, not just the highlights.