The 'one hand' could be any generic hand (no article) or a specific one (definite article). 'The other' refers to the 'matching hand' of the first one. There can only ever be one, and it is being referred to explicitly as the partner of the first, therefore it needs a definite article.
How one and one's is different from other indefinite pronouns The possessive of one (one's) is formed the same way as the possessive of other indefinite pronouns, such as someone (someone's), but it is used a bit differently. For most people, one is consistently used with the possessive form one's.
Both 'a single' and 'one single' are correct and commonly used phrases in English. They are interchangeable and can be used to emphasize the singularity of an item or person.
The difference is that "one" puts more emphasis on the number such as I have 4 computers and a printer/I have 4 computers and only one printer. So when you say a feature of my work or one feature of my work, it means the same, with the only difference that "one" is emphatic compared to "a".
Deadline: Universal Warns “If We Don’t Act Now, Love Will Leave Theaters Forever” — But Says There’s “Hope” For The Rom-Com In Will Gluck’s ‘One Night Only’
Gluck directed One Night Only from his own script — a rewrite of an original from Travis Braun, which topped the 2024 Black List. Pic marks his return to the rom-com genre after titles such as Easy A, ...
Universal Warns “If We Don’t Act Now, Love Will Leave Theaters Forever” — But Says There’s “Hope” For The Rom-Com In Will Gluck’s ‘One Night Only’