In general, there are 2 kind of encounters but in Mega Adventure, Overworld Encounter is a new way to battle/catch Pokemon. Below is a list of Encounters in 3 different ways.
Overworld Encounter
These Pokemon are moving around the map, you can interact with them.
Fateful Encounter
Fateful Encounters are mostly Legendary Pokemon.
Location
Pokemon
Level
Descent Tower's Entrance
Rayquaza
70
Between Route 1 - Corrda
Xerneas
60
Route 13
Yveltal
60
Rocky Cave
Zygarde
60
Koriyama Cave [UG]
Volcanion
60
7th GYM
Diancie
60
Gracidea Meadow
Shaymin
50
Wild Encounter
Route 1
Grass
Day
Night
Rattata
21%
40%
Pidgey
21%
-
Sentret
10%
-
Poochyena
10%
-
Zigzagoone
10%
-
Starly
10%
-
Bidoof
5%
-
Patrat
5%
-
Lillipup
4%
-
Purrloin
4%
-
Hoothoot
-
40%
Spinarak
-
20%
Corrda Forest
Grass
Day
Night
Caterpie
30%
20%
Weedle
30%
20%
Venonat
-
20%
Metapod
10%
Kakuna
10%
Spinarak
5%
Ledyba
5%
Wurmple
4%
Sewaddle
4%
Venipede
1%
Kricketot
1%
-
Hoothoot
-
1%
Route 2
Grass
Day/Night
Ekans
20%
Buneary
20%
Geodude
20%
Drifloon
10%
Nosepass
10%
Nidoran ♂
5%
Nidoran ♀
5%
Roggenrola
4%
Shinx
4%
Seedot
1%
Onix
1%
Route 3
Grass
Day/Night
Surf
Fishing
Nidoran ♂
20%
Goldeen
Nidoran ♀
20%
Carvanha
Aipom
20%
Feebas
Taillow
20%
Magikarp
Marill
10%
Basculin
Mankey
10%
-
Seaking
Route 4
Grass
Day/Night
Surf
Fishing
Snubbull
20%
Magikarp
Shinx
20%
Basculin
Mankey
10%
Abra
10%
Pichu
10%
Nincada
10%
Budew
10%
Croagunk
4%
Dwebble
4%
Riolu
1%
Scraggy
1%
Route 5
Grass
Day/Night
Slowpoke
20%
Mareep
20%
Yanma
10%
Nincanda
10%
Budew
10%
Sewaddle
10%
Venipede
10%
Stunky
5%
Glameow
5%
Pine Forest
Grass
Day/Night
Caterpie
20%
Weedle
20%
Metapod
10%
Kakuna
10%
Wurmple
10%
Sewaddle
10%
Venipede
10%
Cascoon
5%
Silcoon
5%
Route 6
Grass
Day/Night
Surf
Fishing
Bellsprout
20%
Magikarp
Grimer
20%
Basculin
Pineco
10%
Lotad
-
Slakoth
10%
Buizel
-
Budew
10%
Pidove
10%
Lotad
10%
Woobat
10%
Rocky Cave
Pokemon
Chance
Sandshrew
20%
Zubat
20%
Geodude
10%
Aron
10%
Roggenrola
10%
Machop
10%
Makuhita
10%
Woobat
4%
Dwebble
4%
Onix
1%
Riolu
1%
Pure Tower
Pokemon
Chance
Gastly
20%
Koffing
20%
Grimer
10%
Sableye
10%
Shuppet
10%
Banette
10%
Gothita
5%
Elgyem
5%
Misdreavus
4%
Murkrow
4%
Solosis
1%
Litwick
1%
Eleton Path
Grass
Day/Night
Magnemite
10-20%
Mareep
10-20%
Plusle
10%
Minun
10%
Blitzle
5%
Voltorb
5%
Emolga
5%
Pachirisu
5%
Eleton Cave
Pokemon
Chance
Magnemite
30%
Voltorb
30%
Aron
10%
Klink
10%
Ferroseed
5%
Bronzor
5%
Tynamo
4%
Joltik
4%
Emolga
1%
Drilbur
1%
Route 7
Grass
Day/Night
Oddish
20%
Foongus
20%
Snubull
10%
Bellsprout
10%
Ralts
10%
Budew
10%
Sewaddle
5%
Seedot
5%
Lotad
4%
Shroomish
4%
Snivy
2%
Aerocliff Bridge
Pokemon
Day/Night
Pidgey
20%
Pidove
20%
Poochyena
10%
Zigzagoon
10%
Rattata
10%
Ekans
10%
Mankey
5%
Starly
5%
Sentret
4%
Hoppip
4%
Aipom
1%
Seedot
1%
Route 8
Grass
Day/Night
Lopunny
20%
Bibarel
20%
Linoone
20%
Herdier
10%
Watchog
10%
Raticate
10%
Furret
10%
Route 9
Grass
Day/Night
Ralts
20%
Flabebe
20%
Clefairy
20%
Slowpoke
20%
Dedenne
20%
Marill
4%
Kirlia
4%
Audino
4%
Floette
4%
Windflow Bridge
Pokemon
Day/Night
Pidgey
20%
Starly
20%
Spearow
10%
Pidove
10%
Ducklett
10%
Staravia
10%
Pidgeotto
10%
Swanna
5%
Fletchling
5%
Misty Island
Grass
Day/Night
Poliwag
20%
Lotad
20%
Tympole
10%
Buizel
10%
Wooper
10%
Panpour
10%
Poliwhirl
5%
Lombre
5%
Palpitoad
4%
Quagsire
4%
Absol
2%
Descent Path
Grass
Day/Night
Pidgeotto
20%
Emolga
20%
Staravia
20%
Tranquill
20%
Fletchinder
10%
Flabebe
5%
Hawlucha
5%
Descent Tower
Route 10
Grass
Day/Night
Surf
Fishing
-
-
Clauncher
Magikarp
-
-
Skrelp
Basculin
-
-
Buizel
Carvanha
-
-
Shellos
-
-
-
Frillish
-
Route 11
Grass
Day/Night
Surf
Fishing
-
-
Clauncher
Magikarp
-
-
Alomomola
Feebas
-
-
Poliwag
-
-
Poliwhirl
-
-
Seadra
Remoraid
-
-
-
Carvanha
-
-
-
Finneon
-
-
-
Dratini
Route 12
Grass
Day/Night
Surf
Fishing
Krabby
30%
Clauncher
Magikarp
Tympole
20%
Alomomola
Feebas
Palpitoad
30%
Poliwag
Stunfisk
20%
Poliwhirl
-
-
Seadra
Remoraid
-
-
-
Carvanha
-
-
-
Finneon
-
-
-
Dratini
Route 13
Grass
Day/Night
Kirlia
20%
Gothorita
20%
Kadabra
20%
Bronzor
10%
Solosis
10%
Duosion
10%
Espurr
4%
Elgyem
4%
Slowbro
1%
Spiritomb
1%
Route 14
Grass
Day/Night
Sandlash
20%
Carbink
20%
Lairon
20%
Ursaring
10%
Pangoro
10%
Miltank
10%
Nidorina
4%
Nidorino
4%
Rockruff
2%
Route 15
Missing Point
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Mt.Snarlet
Pokemon
Cave
Surf
Grass
Nidoking
Seadra
Lycanroc(Midnight)
Nidoqueen
Basculin
Lycanroc(Midday)
Druddigon
Gyarados
Absol
Fraxure
Lapras
Skamory
Pupitar
Dratini
Braviary
Exploud
Onix
Hariyama
Diggersby
Mawile
Graveler
Magnezone
Probopass
Boldore
Barbaracle
Machoke
Excadrill
Lairon
Steelix
Gabite
Flygon
Aggron
Noivern
Haxorus
Garchomp
Sliggo
Altaria
Shelgon
Goodra
Dragonair
Jangmoo
Tyranitar
Metagross
Dragonite
Route 16
Grass
Day/Night
Medicham
20%
Amoonguss
20%
Houndoom
10%
Camerupt
10%
Absol
10%
Skuntank
10%
Bouffalant
5%
Lycanroc (Midday)
5%
Diggersby
4%
Lickilicky
4%
Zoroark
1%
Ditto
1%
Route 17 (v1.3)
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Oh please, you really think it will be spilled? Haaeel nawh~
Wink wonk~