There are 24 Achievements in ROUNDS and if you grind them you can have 100% in under 2 hours.

All Achievements are possible solo IF you have a spare controller lying around which will allow you to play local matches, that's how I got all mine.

Before the November update certain Achievements could be unlocked in sandbox. Suspiciously, none of the new Achievements unlock in sandbox. If you aren't getting the certain Achievements in sandbox let me know in the comments. All Achievements will unlock in Local Play & Online Play.

I've put these all at the end of the guide since you'll want to work on these last.

Fire a bullet with over 350% projectile speed

Achievable in sandbox

Spawn FASTBALL 2X and fire.

Heal 500 HP in one round

NOT Achievable in sandbox

Equip HEALING FIELD and carefully damage yourself with your own bullets, then heal back to full by blocking. Repeat til success.

Have 4 cards that interact with your block

Achievable in sandbox

Unsure if spawning the same card four times works.
Cards:

• DEFENDER
  
• ECHO
  
• EMP
  
• EMPOWER
  
• FROST SLAM
  
• HEALING FIELD
  
• IMPLODE
  
• OVERPOWER
  
• RADAR SHOT
  
• etc.

Have 30 of your own bullets on screen at the same time

Achievable in sandbox

Get 3 SPRAY and fire away from terrain to keep your bullets from despawning.

You can also get MAYHEM and DEMONIC PACT to make it easier.

Block 10 times in 10 seconds

Achievable in sandbox

TELEPORT and DEFENDER both reduce the block cooldown by 30% so 5 cards of them should be enough.

Pick 3 or more rare cards in one match

NOT Achievable in sandbox

This Achievement just happens over time. The only tip is knowing what makes a card rare; Purple filled-in corners denote rare cards. The coloured outline or text of a card is irrelevant.

Fun fact the three rarities are: Common (empty corners), Uncommon (blue corners), Rare (purple corners).

Deal 500 DMG with one bullet

Achievable in sandbox

Stack five of the following and land a hit on your enemy:

• CAREFUL PLANNING
  
• COMBINE
  
• GLASS CANNON
  
• WIND UP

Reach 1000 HP

Achievable in sandbox

The TANK card gets you the most hp so spawn that if 5 or so times.

Use Remote 3 times in a single match

NOT Achievable in sandbox

REMOTE is a rare card so it may take a while but once you have it shoot and control you bullet three times during a match which is easy.

Use Phoenix

NOT Achievable in sandbox

PHOENIX is a rare card so it may take a while but once you have it: die by any means which will respawn you.

Use Frost Slam 20 times

NOT Achievable in sandbox

FROST SLAM is a common card so easy to find but look out for DEFENDER and TELEPORT to speed up your 20 blocks.

Use Saw

NOT Achievable in sandbox

Block with the SAW rare card.

Use Teleport 3 times in a single match

NOT Achievable in sandbox

Block with the TELEPORT rare card three times in a match.

Use Supernova 3 times in a single match

NOT Achievable in sandbox

Block with the SUPERNOVA rare card three times in a match.

Use Demonic Pact 3 times in a single match

NOT Achievable in sandbox

Shoot with DEMONIC PACT rare card three times in a match.

This rare card took me forever to find but I was probably just unlucky.

Use Radiance 3 times in a single match

NOT Achievable in sandbox

Reload three times with the RADIANCE rare card.

Fun fact this Achievement is misspelled, it should be Radiant.

Trigger a block with Shields Up

NOT Achievable in sandbox

The SHIELDS UP rare card triggers automatically upon firing your last bullet.

Win 5-0 & Lose 0-5

NOT Achievable in sandbox

If you are playing a local match by yourself with a spare controller just suicide one of your characters to lose 0-5. The other character will win by 5-0. You will be given both achievements.

I'd imagine Ace wouldn't be too hard in ONLINE PLAY if you practised a lot.

NOT Achievable in sandbox

Now all five of these achievements are going to be unlocked by grinding Champion. You can also pursue all the other card specific Achievements while using this method but it won't be as fast.

You will need two computer inputs (e.g. Keyboard & controller) which will allow you to host a LOCAL PLAY session just by yourself. What you are going to do is continuously suicide one of the characters into the border. Preferably aim for the close bottom corner as you can use the damage push back to fly into the other death barrier. At the absolute fastest you can end a round-half in under a second (seriously). With a total of 50 matches (250 rounds or 500 round-halves) needed for Champion this method got me the Achievement in less than an hour.

Now if you are struggling with some of the rare cards then you may want to pay attention while grinding Champion as you will be shown 1,250 cards over the 50 rounds minimum. TIP The Rare purple corners are shown even on the backside of cards so you will know at a glance if it's rare.

If you have gotten all other Achievements then the card selection phases will only slow down your pace. This is because of cards which give your character health and make suiciding slower (especially when stacked), here's a list of all cards to avoid:

• DEFENDER
  
• ECHO
  
• EMP
  
• FROST SLAM
  
• HEALING FIELD
  
• HUGE - very bad, makes suicide 4 shot instead of 2.
  
• IMPLODE
  
• LIFESTEALER
  
• OVERPOWER
  
• PARASITE
  
• PHOENIX - the worst, plays an animation every time you die, not worth the health reduction
  
• PRISTINE PERSEVERANCE
  
• RADAR SHOT
  
• RADIANCE
  
• SAW
  
• SHOCKWAVE
  
• SILENCE
  
• STEADY SHOT
  
• SUPERNOVA
  
• TANK - very bad, makes suicide 4 shot instead of 2.

I found the fastest strategy was to pick the first card that didn't give me HP. Although if you want, there are a few cards which will weaken you on the way to the border:

• DEMONIC PACT - firing makes you lose 10HP, it can't kill you but will make you die quicker.
  
• EXPLOSIVE BULLET - fire at your feet for maximum effect, in theory the quickest way to die.
  
• GLASS CANNON - the only card worth looking for imo, makes the border a 1 shot.

If you've followed this guide you've probably gotten all 24 Achievements without too much time spent on Champion Congratz.

This is my first guide I've made on steam so any engagement is appreciated.