Word or phrase for a disproportionately strong measure
Solution 1:
Some examples come to mind. The one I use most frequently is
"You don't swat a fly with a sledgehammer."
And I do recall reading one in Robert Heinlein's sci-fi novel The Moon is a Harsh Mistress in which one of the characters says
"You don't spank a baby with an ax."
That sounds a bit over the top (I wouldn't spank a baby with anything, much less an ax) and makes me queasy. Which is why I use the fly/sledgehammer trope.