Here is the full list of all 80 MARVEL END TIME ARENA achievements.
Hero & Skin Count 5
User Level 15
Hero & Skin Count 10
Hero & Skin Count 20
Kill Count 10
MVP Count 1
Play Count 6
Win Count 3
Arena Point 10000
User Level 30
User Level 40
User Level 50
User Level 70
User Level 90
User Level 110
User Level 140
User Level 170
User Level 200
Arena Point 20000
Arena Point 30000
Arena Point 40000
Arena Point 50000
Arena Point 60000
Arena Point 70000
Arena Point 80000
Arena Point 90000
Arena Point 100000
Hero & Skin Count 30
Hero & Skin Count 40
Hero & Skin Count 50
Hero & Skin Count 60
Hero & Skin Count 70
Hero & Skin Count 80
Hero & Skin Count 100
Kill Count 50
Kill Count 100
Kill Count 200
Kill Count 400
NEW_ACHIEVEMENT_DESC_17_8
NEW_ACHIEVEMENT_DESC_17_9
NEW_ACHIEVEMENT_DESC_17_10
NEW_ACHIEVEMENT_DESC_17_11
NEW_ACHIEVEMENT_DESC_17_12
NEW_ACHIEVEMENT_DESC_17_13
NEW_ACHIEVEMENT_DESC_17_14
NEW_ACHIEVEMENT_DESC_17_15
NEW_ACHIEVEMENT_DESC_17_16
NEW_ACHIEVEMENT_DESC_17_17
NEW_ACHIEVEMENT_DESC_17_18
NEW_ACHIEVEMENT_DESC_17_19
NEW_ACHIEVEMENT_DESC_17_20
NEW_ACHIEVEMENT_DESC_17_21
NEW_ACHIEVEMENT_DESC_17_22
NEW_ACHIEVEMENT_DESC_17_23
NEW_ACHIEVEMENT_DESC_17_24
NEW_ACHIEVEMENT_DESC_17_25
NEW_ACHIEVEMENT_DESC_17_26
NEW_ACHIEVEMENT_DESC_17_27
NEW_ACHIEVEMENT_DESC_17_28
NEW_ACHIEVEMENT_DESC_17_29
NEW_ACHIEVEMENT_DESC_17_30
NEW_ACHIEVEMENT_DESC_17_31
NEW_ACHIEVEMENT_DESC_18_0
NEW_ACHIEVEMENT_DESC_18_1
NEW_ACHIEVEMENT_DESC_18_2
NEW_ACHIEVEMENT_DESC_18_3
NEW_ACHIEVEMENT_DESC_18_4
NEW_ACHIEVEMENT_DESC_18_5
NEW_ACHIEVEMENT_DESC_18_6
NEW_ACHIEVEMENT_DESC_18_7
Accumulative number of kill assisting : 20
Accumulative number of kill assisting : 100
Accumulative number of kill assisting : 200
Accumulative number of kill assisting : 400
Accumulative number of kill assisting : 800
Accumulative number of kill assisting : 1600
Accumulative number of kill assisting : 3200
Accumulative number of kill assisting : 6400
Accumulative number of kill assisting : 12800
Accumulative number of kill assisting : 25600