1a. We all unite as one to oppose the government scheme.
1b. We all unite in one to oppose the government scheme.
2a. Father, Son and Holy Spirit unite in one to form the Trinity.
2b. Father, Son and Holy Spirit unite as one to form the Trinity.
Please correct the above sentences.
Thanks.
‘… as one…’ is the correct preposition in both cases.
Many bodies (etc.) coming together so closely it’s as if they were one body.