The 4th Way

Leadership has the deepest card selection of all the aspects with several different playstyles possible within the cards available. This puts it at the far end from Justice which has approximately one way to play it.* Contrast Leadership where I have 3 fully viable, none overlapping decks - cheap recyclable swarm, powerful allies with attachments and all the big allies you can pay for. This deck uses a 4th take - buffing the Hero. The allies providing emergency blocking/thwarting/damage but also power Strength In Numbers which lets you draw more cards to buff Quicksilver up. I have used the Strength in Numbers thing before but the advent of Quicksilver, where every buff is used at least twice, makes that side of things much more appealing.

Note there are at least two more archetypes to try with Leadership; buffing your team with Lead from the Front and Avengers Assemble! and buffing as you flip with Antman or Wasp, though I guess that may be a special case of this style of deck. (also Teamwork engines) . These may or may not be viable (yet?)

So this deck has a swathe of cheap allies with the standard Make the Call to recycle them. They contribute a bit of thwarting and damaging and some chump blocking but you really want to get 3 or more of them into play. This makes Strength In Numbers very appealing. You use Morale Boost and Maximum Velocity to buff Quicksilver then his innate ability and Always Be Running (RIP Netrunner) make repeated use of the buff. Sometimes the stars align and you get to use Moxie. In fact the Moxies could usefully be another card, maybe honorary avenger to extend the use of the allies and thin a bit.

It is not a top tier deck - it is a bit fragile and never really feels super set up. That is even with 4 or 5 allies and most of its support/upgrades in play. It is especially weak to Under Attack and the encounter card that pings all characters for one damage. Concussive Blast

Cards

Quicksilver is a standard human with one extra HP. He has the terrible 1 1 1 stat line but with his ability to untap twice per turn gets much better value from this (being effectively 2-2 2 with one point of damage protection) and he really takes buffs well. His Alter Ego ability is pretty underwhelming - substantially better if you have his sister along MP. His hero ability super speed is utterly defining. As well as the obvious double thwart/attack options he also gets to defend for free once per turn. This may still be ill-advised against a brute like Rhino but is good for tanking low damage minions for ages.

Scarlet Witch She is a poor ally as her output is random. If you think of her as being 2 THW and ATT who lets you down occasionally you will not go far wrong. She is best at thumping the villain or main scheme as you will not over kill it often and shortfalls are not so annoying as on side schemes or minions. It is sweet when she hits a Hydra Regular for 4 though.

Serval Industries This card does not give direct card advantage like many hangouts but it does let you recycle your best cards - these are usually Always Be Running and Speed Cyclone. You can also get second chance at an upgrade you had to pitch. It plays much better than I expected it to and you can jam the back half of your deck with cards that give you really good turns.

Friction Resistance This is an amazing resource generation card. It is a little expensive, in this deck, to play out but once it is out it can usually generate 2 resources a turn and often 3-4. The timing can get confusing - as you can play Always be Running for free and get one other free untap you can often play a lot of cards which can be tricky to plot out. His best card and definitely not one to turn into a resource unless you are going to die.

Speed Cyclone His defensive card. Solo this mostly stuns the villain for one resource, ideally the one left over from Friction Resistance. This is of course a very easy card to play. It is very useful and good to recycle with Serval Industries.

Accelerated Reflex. It is fine to increase defence and all but still risky to block and this is more expensive than the aspect version so probably his worst card (and it's not bad as such just a bit awkward and slow). Often he will be blocking 1 attack minions or he will have a couple of points of boost from elsewhere so the extra here is not very useful.

Reinforced Sinew This is probably his most useful upgrade solo as you always need damage but you can make do with lower thwart. Exactly duplicates the aspect version which is sad but still OK

Hyper Perception Extra thwart is great but not always needed. One reason to play all these upgrades is that it does thin your deck as well as providing the buffs and there is not a lot of other deck thinning here.

Always Be Running is a defining card. He only has one more copy than Spider Woman and her glides but he can play it for almost free with Friction Resistance while she cannot get a discount on hers within her signature cards. It lets you make good use of stat buffs and if you stack a thin deck with lots of them gives you very entertaining turns.

Maximum Velocity This is a double strength Morale Boost for only 50% more cards. It gives you very solid stats for a turn especially as you get to use them 3+ times. It is a little awkward to play compared to Morale boost and not worth playing ahead of an upgrade except, as ever, in emergencies. Essentially it can be hard to get full value out of all the boosts so is not quite as amazing as it first appears. It is still very good though.

Double Time is at worst a slightly improved Haymaker and at best a slightly improved For Justice, or a very handy combination of the two. It is extremely flexible which means it is often good to play it. While you may get more theoretical value out of Maximum Velocity this can be more precise. It does not get played every time you have it (unlike Speed Cyclone but exceeded my expectations.

Avalanche is Quicksilver's nemesis and are worth noting. He and his scheme are easy to remove once in play but have a dangerous immediate impact. He turns up with incite 2 and the Extortion of Seismic Proportion side scheme which adds another 1 threat from incite. This along with 2 indirect damage or tapping is pretty bad, like drawing Advance plus extra nasties. Two cards he puts into the encounter deck are also unpleasant. Earthquake has incite 1 and causes you to tap and discard 2 cards which is a big tempo hit. Vibration Resistance his last card is weak - reducing damage the subject takes but very easy to remove by just tapping.

*solo at least; I suspect there may be a very heavy thwart build that would work in Multiplayer.