Tony Abbott has admitted he made unnecessary enemies and left his friends feeling under-appreciated during his time as prime minister, as part of an extraordinary mea culpa on his government's failings.

While Mr Abbott used his first two essays for Quadrant magazine to explain and defend his legacy, in the third and final instalment of the series, he spends some time candidly reflecting on where he and his government went wrong.

He admits "there were some issues the Abbott government could have managed better or not pursued at all".