a (lone) voice in the wilderness

if you are a voice in the wilderness, you are the only person expressing a particular opinion, although later other people understand that you were right.

With her passionate pleas for peace, she was a lone voice in the wilderness.

• a marked man
• a marriage made in heaven
• a match made in heaven
• a matter of
• a matter of doing something
• a matter of life and death
• a matter of life or death
• a matter of opinion
• a matter of record
• a matter of something
• a matter of time
• a meal ticket
• a means to an end
• a medallion man
• a meeting of minds
• a meeting of the minds
• a melting pot
• a merchant of doom
• a mess of
• a mess of something
• a middle-aged spread
• a mile a minute
• a mile away
• a mile off
• a millstone around neck