@roxy not exactly. You're thinking of Adventure 01 where two such protagonist partners DID turn into those;

[Patamon -> Angemon]

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Arguably; [Agumon -> Greymon -> MetalGreymon -> WarGreymon] as well as [Gabumon -> Garurumon -> WereGarurumon -> MetalGarurumon] DO look robotish due to the armor they basically gain.

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You may have been thinking of Datamon; an antagonist that was very soon after the File Island arc of the season