To All the Slimes I Love

/way #2214 57.48 67.64 Spring Mole
/way #2214 64.53 32.38 Lightdarter
/way #2214 42.01 16.38 Dustcrawler Beetle
/way #2214 58.79 68.61 Grottoscale Hatchling
/way #2214 48.50 12.57 Lava Slug
/way #2214 72.85 39.65 Cavern Skiplet
/way #2214 42.01 16.38 Cavern Mote
/way #2214 54.41 34.73 Darkgrotto Hopper
/way #2214 59.40 45.92 Pebble Scarab
/way #2214 51.28 15.43 Snake
/way #2214 52.85 54.73 Tiny Sporbit
/way #2214 60.31 92.21 Mass of Worms
/way #2214 54.67 29.92 Crackcreeper
/way #2214 45.78 13.52 Earthenwork Stoneskitterer
/way #2214 57.30 65.74 Moss Sludglet
/way #2214 61.96 30.27 Stumblegrub
/way #2214 67.01 38.78 Oozeling
/way #2214 42.42 14.37 Rock Snail

These are just the places I found mine. There are likely many spawn locations not included on this list and you may not find yours at the locations listed here.

Here is a targeting macro that will target the needed critters for this achievement while fitting in a standard 255 character in-game macro. I had no issues with the short forms targetting random mobs or critters that are not part of the achievement.

/tar Spring
/tar Lightda
/tar Dustcrawler
/tar Grottoscale
/tar Lava Sl
/tar Cavern Sk
/tar Cavern M
/tar Darkgrotto H
/tar Pebble
/tar Snake
/tar Tiny S
/tar Mass of
/tar Crackc
/tar Earthenwork St
/tar Moss Sl
/tar Stumbleg
/tar Ooze
/tar Rock S

New Coordinates for 11.1 (Shifted by 4 on the X Axis, Original Coordinates taken from @YariniCeteri

The 4 Coordinate shift worked relatively well, though not entirely.
Edit: Added all and checked, should be correct now.

/way #2214 53.48 67.64 Spring Mole
/way #2214 60.53 32.38 Lightdarter
/way #2214 38.01 16.38 Dustcrawler Beetle
/way #2214 54.79 68.61 Grottoscale Hatchling
/way #2214 44.50 12.57 Lava Slug
/way #2214 69.26 41.66 Cavern Skiplet (Around that area)
/way #2214 38.01 16.38 Cavern Mote
/way #2214 50.41 34.73 Darkgrotto Hopper
/way #2214 55.40 45.92 Pebble Scarab
/way #2214 47.28 15.43 Snake
/way #2214 48.85 54.73 Tiny Sporbit
/way #2214 56.31 92.21 Mass of Worms
/way #2214 50.67 29.92 Crackcreeper
/way #2214 41.78 13.52 Earthenwork Stoneskitterer
/way #2214 53.30 65.74 Moss Sludglet
/way #2214 57.96 30.27 Stumblegrub
/way #2214 60.84 41.43 Oozeling (Cave Entrance, go in)
/way #2214 38.42 14.37 Rock Snail

Sorted by y-coordinates so you start at the top of the map and work your way down and won't be doubling back.

New Coordinates for 11.1 (Shifted by 4 on the X Axis, Original Coordinates taken from @YariniCeteri

The 4 Coordinate shift worked relatively well, though not entirely.
Edit: Added all and checked, should be correct now.

/way #2214 44.50 12.57 Lava Slug
/way #2214 41.78 13.52 Earthenwork Stoneskitterer
/way #2214 38.42 14.37 Rock Snail
/way #2214 47.28 15.43 Snake
/way #2214 38.01 16.38 Dustcrawler Beetle
/way #2214 38.01 16.38 Cavern Mote
/way #2214 50.67 29.92 Crackcreeper
/way #2214 57.96 30.27 Stumblegrub
/way #2214 60.53 32.38 Lightdarter
/way #2214 50.41 34.73 Darkgrotto Hopper
/way #2214 60.84 41.43 Oozeling (Cave Entrance, go in)
/way #2214 69.26 41.66 Cavern Skiplet (Around that area)
/way #2214 55.40 45.92 Pebble Scarab
/way #2214 48.85 54.73 Tiny Sporbit
/way #2214 53.30 65.74 Moss Sludglet
/way #2214 53.48 67.64 Spring Mole
/way #2214 54.79 68.61 Grottoscale Hatchling
/way #2214 56.31 92.21 Mass of Worms