Going into Afghanistan behind behind the Bush administration and without a plan was a mistake… but after 9/11 and with the Taliban sheltering bin Laden, it was a pretty much a politically inevitable mistake.
Iraq could and should have been avoided. Saddam Hussein was horrible piece of faeces (although the circumstances that allowed his rise to power were largely created by botched British ‘nation building’), but the spurious justifications and predictable failures hugely taint Blair’s legacy. As do his embrace of the excesses of financialisation of the economy associated with the 2008 crash and stuff like standing godfather to one of Murdoch’s progeny.
As for his knighthood, it is pretty much up with the rations for ex-PMs. I only went back as far as Wilson, but he Heath, Callaghan, Thatcher and Major all got KGs too. I wouldn’t be surprised if Brown, Cameron, May and Johnson get them in time. The whole system needs reforming and perhaps updating to get rid of the callbacks to the language of feudalism.