The ignition coil would kill 2 plugs if it went bad (UNLESS A SHORT TO GROUND DEVELOPED IN THE COIL RIGHT NEXT TO THE CONNECTOR FOR THE # 2 CYLINDER PLUG WIRE. Then it would only stop the spark to # 2 cylinder). Sometimes an engine can miss on two different cylinders, but may sound like it only misses on one. If you could exchange the position of the two plug wires on that coil section (the two connectors which are straight across from each other); you could see whether the # 2 cylinder still is the one that is bad; or whether the problem has moved to the other cylinder.
My suspicion is that this is either a compression problem, or the fuel injector for the # 2 cylinder has stopped working. If a cylinder has low compression, or the injector is not supplying fuel; the spark to that cylinder can look very different from the other cylinder. I also don't know how you connected the spark detector, or what kind of device it is; but there may have been a problem with the way you used it.
The first thing I would do is to test the compression in cyl # 2. If it is less that 135 psi; there is a mechanical problem in that cylinder (blown head gasket, broken piston, or burned or stuck valves). If the compression is good; I would test the power wire to the # 2 fuel injector for trigger pulses with a 'noid light (which can be bought or rented from most parts stores). If there are no trigger pulses to the # 2 cylinder injector; the injector wiring harness must be tested and repaired. If there are trigger pulses to that injector; replace the fuel injector for that cylinder.