The O.P.S. Zeal

• Wave 1 - Defeat the wave using Sky-Line strikes only
  • Easy mode. Just pounce on everyone from a skyline. Bear in mind that you can pounce from the stationary crane hooks, too.
• Wave 2 - Defeat the wave while only taking shield damage
  • A little more tricky if you haven't purchased any upgrades yet. Hang back behind cover and let your shield regenerate if you get hit. If you're quick with the sniper rifle, you can pop all the enemies before they get near you.
• Wave 3 - Defeat the wave using only the Sky-Hook attacks and Shotgun
  • Put some fools in the ground with the streetsweeper. Skyline strikes count as Sky-Hook attacks so make use skylines to instakill enemies. Both the standard shotgun and Vox blunderbuss are valid weapons for this challenge.
• Wave 4 - Defeat the wave using only machine guns or the crank gun
  • Either the Founder or Vox machinegun will do here. Both types are scattered around the level in Tear barrels. Be careful not to use the Vox carbine (big glass sight with an X in it) as it doesn't count as a machinegun and will cause you to fail the challenge. I have no idea where you'd get a crank gun at this point.
• Wave 5 - Defeat the wave using only the pistol and hand cannon
  • One Handyman and you can only use pistols. Make sure you really only use pistols. Hitting him with any Vigors will invalidate the challenge conditions. Aim for the head or heart if you can and keep on the move. If you bait the Handyman into shocking the skyline you can get a couple free hits in on his heart. Upgrading the damage on the handcannon makes this fight go faster.
• Wave 6 - Defeat the wave without picking up weapons or looting corpses
  • A relatively easy challenge compared to the last. Make sure you bring the guns you want with you and keep on the move to avoid the rocket soldiers. If you're quick, you can shoot the rockets out of midair, doing so and killing the soldier who shot it with the blast will earn you an achievement.
• Wave 7 - Defeat all enemies using only zoomable weapons while they are zoomed
  • This one's tricky since all your kills need to be made while zoomed in. Bear in mind that any weapon you can zoom wtih works here. Like the handcannon or rocket launcher. The Crow is the only enemy that gave me trouble in this wave. Fortunately, he doesn't have AI to deal with you while you're riding a skyline. Hop on and plug him in the head with some scoped shots.
• Wave 8 - Defeat all enemies using only Tears; Possession Traps; and Return to Sender traps
  • Kind of a pain in the ass as the Tears in the area generally suck at killing anything, fortunately there are only four enemies. Be sure that you're using the trap version of Possession and Return to Sender; the regular version will make you fail the challenge. Both the grenadiers and Crows are equally adept at dispatching each other, so drop a Possesson trap and use the tesla coil or mounted gun Tears on the survivor.
• Wave 9 - Defeat all enemies without ever hitting anyone in the head or the heart
  • Here you're facing a handful of soldiers and a Handyman. As long as you don't get any headshots or hit the Handyman in the Handyheart, you pass. From what I've tested, it's impossible to get a head/heart shot with vigors or explosives, so if you really want to avoid any accidents take some weapons that go boom. Charge is good for the mobility it provides when cleaning up the soldiers and crows also seem really effective in OPS Zeal. Deal with the soldiers first, then kite the Handyman around the level and toss some high-explosive ordinance at it whenever you get a clear shot.
• Wave 10 - Defeat the Siren before she performs a resurrection
  • This is the first ragequit level in CitC. The Siren always spawns directly ahead and to the right of your start position. You have maybe ten seconds to drop the her before she moves in and finishes her resurrection animation. The damage-upgraded Hailfire is your best friend here: drop off the ledge and don't stop your assault until the challenge completion logo pops up.
• Wave 11 - Defeat the wave without using Sky-Lines or Hook-points.
  • A Fireman, Patriot, and a lone dude possibly named Clarence. The difficulty in this challenge comes from being grounded the whole time. Both the Patriot and Fireman spawn on the deck above you, go up the left stairs to attract the attention of the Fireman and separate him from the Patriot, you don't want to be fighting both at once. The Hailfire works equally well on everything here as it did on the Siren but you can conserve ammo by using Undertow to toss the Fireman off of the level. Now that it's a fair fight, taking down the remaining baddies should be straightforward.
• Wave 12 - Defeat the wave within 1:15
  • You're up against a pair of Firemen and a pair of Crows this time. Undertow can trivialize this fight if you position yourself correctly. If you upgraded your tentacles to pull multiple enemies at a time, you can snatch both Firemen and one Crow off of the top deck and plop them over the edge before they even notice you. You've now got 70 seconds to decide how you want to finish the remaining Crow.
• Wave 13 - Defeat the wave using only weapons fired from a Sky-Line or Sky-Line strikes.
  • Two Firemen and a Handyman: Finish them. Hanging from skylines the whole time means no Vigors but that doesn't mean this fight is difficult. Zoom around on the rail taking whatever shots you can until the Handyman jumps up and tries to shock you off. Then transfer to one of the statonary hooks and keep up your assault. Tears are fair game as long as they aren't ones that deal damage so make use of the Decoy Tear if you need a breather.
• Wave 14 - Defeat the wave using only Shock Jockey and Headshots
  • Here's another potential Frustration Wave since it comes so late in the series. Lining up headshots is tough when enemies are spazzing around from being shocked. If you get close and aim slightly above their heads you can minimize an accidental neck/shoulder kill. Or you can dispense with Shock Jockey altogether and use the sniper rifle from afar. Just make sure every kill is with a headshot.
• Wave 15 - Defeat each enemy with a different Vigor type (until you have used all Vigor types
  • This is my least favorite wave in OPS Zeal since the conditions aren't really that clear and you need to replay all 15 levels if you fail the challenge. From what I can tell, using Vigor types just means landing the killing blow on each enemy with a different Vigor. You're fighting two Handymen and a Patriot this wave, so soften each of them up with some conventional firepower first. Kill the Patriot with Shock Jockey if you can since the Handymen are resistant to it. I used Devil's Kiss and the oil spill Tear to down one Handybro and Charge to take out the other, but I'm sure there's a faster way. As always, use the skylines to make sure you're not fighting against more than one enemy at a time and use cover to let your shield recharge. This is mostly a battle of attrition so take it slow and make your attacks count.