As one of the main architects of the Good Friday Agreement it was his involvement, along with that of Gerry Adams, that gave the process legitimacy in the eyes of the Republican community, and without that it simply would not have happened.
And his political career was remarkable, building on that peace process – who can forget his unlikely cordiality with former enemy Ian Paisley, or his meeting with the Queen in 2012.
But equally who can forget the outrages perpetrated by the IRA, of which he was a commander. The terrorists murdered British soldiers on the streets of British cities using the bullet and the bomb. The bullet was almost always delivered from a distance from a place of concealment – rarely did IRA volunteers put themselves at risk or engage in open confrontation. Sometimes the bombs were delivered by civilians forced to drive the explosives to their target.
And it was not just soldiers or alleged traitors to their cause they killed. The ruthless and brutal IRA bombing campaign killed scores of innocent victims including children in cities both in Northern Ireland and on the UK mainland. Martin McGuinness was a key part of that deadly campaign.
So his life was perhaps proof that people can change; from armed struggle he embraced peace – the change was profound and genuine. But perhaps – and understandably – not all are able to find forgiveness for his part in many heartless crimes.