Going Under

There are these business cards that you can buy from rooms labeled with an @. After obtaining a blank business card (which does 50 damage), the killing blow has to be done to an enemy with the blank business card in order to obtain the business card of the enemy. During the Cubicle dungeon, the blank business card has to be found in a Cubicle box. I recommend playing the first room before any combats until a business card if found. Other than the business cards, the other two ways you complete the rolodex is by exhausting all dialogue with each shop keeper and the curse bringer (Hauntrepreneur). Notice that any business cards in italics can be found in part 2 of the campaign. A list of all business cards in order and how to unlock is as follows:

Fizzle

1) Jackie Fiasco - owned from beginning
2) Marv - given by Marv at the very beginning
3) Ray - complete all quests
4) Tappi - complete all quests
5) Fern - complete all quests
6) Kara - complete all quests
7) Elijah 'Swamp' Fiasco - complete all quests
8) Eclaire

Joblin

9) Sellsword
10) Freelancer
11) Canbassador
12) Chauffer
13) Rockstar
14) Joblifter
15) The Caffiend
16) Promotor
17) Elite Sellsword
18) Chauffeur Pool
19) 10x Caffiend
20) Jelly - this is the shopkeeper

Winkydink

21) Wimp
22) Winkubus
23) Dinkubus
24) Emoozi
25) Purple Emoozi
26) Big Emoozi
27) Howdy
28) Peepr
29) Hover Hands
30) Blue Emoozi
31) Slime Hand
32) Masked Winkubus
33) Masked Dinkubus
34) Mask Off Hover Hands
35) Lilli - this is the shopkeeper

Styxcoin

36) Miner
37) Detonator
38) Hypeman
39) Josh Patella
40) Blackhat
41) Kilobat
42) Chump Chains
43) Power Loader
44) HuStleboneS
45) Gigabat
46) Rabblerouser
47) Racketeer
48) Ferryman HuStleboneS
49) Zans - this is the shopkeeper

The Hauntrepreneur

50) The Hauntrepreneur - this is the guy that gives you curses in exchange for power-ups

Cubicle

51) Fulfiller
52) Buddy
53) Stocker
54) *Hungry Box* - Hardest card in game for me. Attack all boxes in part 2 of campaign until a hungry box appears and simply kill with a blank business card. This is just a very rare event. I have only encountered the hungry box in part 2 of the campaign or above imposter trial 5.
55) Vested Marv
56) Avie - can be earned in the office on floor 1000 by attacking Avie with a business card

Fizzle

57) The Imposter - Have to use the blank business card on the imposters second form

The above guide by Liebers87 really helped me a bunch in finding what I needed. Just wanted to add a couple of tips that I learned along the way that might be helpful to others.

Overall Technique - I found that focusing on the enemy and hitting X was the best way to get hits on the enemies to network them. Try not to have any power ups equipped that damage enemies while focusing on them or else they could die before you can throw the business card.

Slowing Enemies - Also, having items that slow or freeze enemies can be helpful if they keep jumping or pouncing out of your aim at the last second. I found the Flashmob app to be helpful as I could use the camera flash to temporarily freeze an enemy and then hit them with the card. There is another skill that lets you enter a room disguised. This may help in identifying an enemy before it attacks and gaining a 1-hit kill/network with the card if they are a weaker enemy.

Avie - You can actually just hit Avie on the desk in Cubicle after your fight with Vested Marv. You don't have to wait until the big final battle.

Mask Off Hover Hands - This is the boss of the part 2 version of The Winkydink dungeon. The fight has multiple phases and I learned the hard way, what doesn't count to hit with your business card. In the first phase, you fight his hands. Killing either of these with the card doesn't work. In the second phase, you fight the big slime behind the DJ booth. Killing him doesn't count either. Once you kill this slime, he breaks off into 3 smaller slimes. You have to get you final hit with the business card on the last remaining slime to network the overall boss. Be careful not to accidentally kill all of them initially. I ran around to separate them and killed them individually until there was only one left to kill. Having the dodge roll that slows enemies down helps a lot in not having them jump away at the last minute.