Consider the spell true polymorph. If you turn a creature into a creature, the new creature
retains its alignment and personality.
If you turn an object into a creature
The creature is friendly to you and your companions.
An object typically has neither personality nor alignment, so that isn't normally an issue.
However, a sentient weapon is an object (per Sage Advice), and does have personality and alignment.
If you cast true polymorph to turn a sentient, neutral evil greatsword into a creature, does the creature retain the sword's alignment and personality?
Which could imply that it is not friendly.