Of course the Russian Revolution - that led to peasants eating their own children in the Socialist Utopia.
Of course we would not be sending children down mines if there had been no Left. It was Peel's Tory government that legislated to stop young children and females working underground.
The immense improvements in ordinary peoples' lives has come about due to Capitalism not the Left.
If the Conservatives had won the 1945 General Election there would have been an NHS - they had proposals in their manifesto for a health service that was almost identical to Labour's.
It is one of the great myths that the Left has generated progress.
Firstly, there was no 'left' to talk about in Victorian times; certainly no 'left' party, merely those who supported the poor liberating themselves from the the yoke placed there by the money makers. Any changes were brought about by those who existed within the main political parties. No doubt, as stated above, reviled for doing so by those who thought such measures would decrease profits.
Of course you are correct about the devastating cruelty of communist regimes in he past.
Do you really think the statement you so baldly make is true - really? Certainly the standard of living has increased in this country but if you think that associated improvements in living conditions and the welfare of the poor and disadvantage would have come about within a capitalist society without the promptings and fighting of those who believed in a better life for all, you are misguided.
Directly after the revolution, Churchill and the 'white' army were attempting to overthrow the infant communist regime. Did he do this in order to protect the civil liberties of those in Russia? no, it was to prevent such political thought 'infecting' the rest of Europe, including us. That is, to prevent any political thought that might (would) undermine and obstruct those who owned the wealth here - for their benefit.
The arrest and deportation of the Tolpuddle Martyrs in Dorset , as they met to organise the first trade union is testament to what lengths the money-men were prepared to go to. The fact that the TMs returned to the UK as heroes of the working classes shows us that this movement was ground - based, not the puppet of political left wingers.
Changes in living standards were brought about in this country within a mixed economy of right and left including the trade union movement, whom I suspect you revile as 'commies' or anti - freedom.
So, yes, the left has 'generated' progress. Had it been left solely to the capital men, I would argue that very little progress would have been achieved.