weakling (n.)

• baby
• butt
• castrato
• chicken
• coward
• crybaby
• doormat
• drip
• dud
• eunuch
• fence-sitter
• funk
• gelding
• incompetent
• invalid
• invertebrate
• jellyfish
• lightweight
• mark
• milksop
• misfit
• mollycoddle
• mouse
• mugwump
• namby-pamby
• nebbish
• nonentity
• pansy
• pantywaist
• pushover
• sissy
• softy
• sop
• sucker
• waverer
• wobbler