Was Alexander the Great a visionary genius or a butcher?

He was both. He had a vision of the Persian Empire which he took over being converted to Greek culture which he believed, rightly or wrongly, to be superior. After starting this process he planned taking over western Europe and doing the same, but his early death stopped that.

In the process there was massive slaughter and economic disruption which he pursued relentlessly. Even some of his own generals were victims. Self aggrandisement shared an equal part with his world vision, with him triumphant at the centre.