As usual, Sealion takes the cake. Kerch was the most insane one that was actually carried out, and is actually probably a good model of what would have happened had Sealion actually been attempted. Gallipoli is probably second due to its poor planning and even worse execution.
the actual plan for sealion wasn't insane and the KM made a set of preconditions that where common sense before the op would be considered; and when those where not met, they advised their plan couldn't be launched; that is sober analysis
kerch had NO preconditions for success even considered, they just flung the men into the peninsula for Manstein to crush them with artillery and air strikes
if the germans could land a field army in the UK, that field army would be stronger than any force they would encounter so once established they could realisticly expect to win so long as they could supply
kerch was landing men to face a numericaly superior force which enjoyed vastly superior air and artillery support
it was BY far more insane than the KM's staff study and subsequent recommendation against sealion; sealion proved to be a mental exercise that the Germans thought better of; Kerch sent 100k men to pow cages or their death