For this achievement you have to re-up 10 times. You will need a total of 1.435.500 xp (Re-Up 9 Lvl 100). This should come naturally when you go for all other achievements. However you can boost this if you wish.
First of all:
How much XP do you need?
ReUp - XP/Level - Total XP/ReUp - Cumulative XP - % of Total/ReUp - Cumulative % of Total ,
0 - 1000 - 99000 - 99000 - 0.12% - 0.12% ,
I (1) - 1100 - 108900 - 207900 - 0.13% - 0.25% ,
II (2) - 1200 - 118800 - 326700 - 0.14% - 0.4% ,
III (3) - 1300 - 128700 - 455400 - 0.16% - 0.55% ,
IV (4) - 1400 - 138600 - 594000 - 0.17% - 0.72% ,
V (5) - 1500 - 148500 - 742500 - 0.18% - 0.9% ,
VI (6) - 1600 - 158400 - 900900 - 0.19% - 1.1% ,
VII (7) - 1700 - 168300 - 1069200 - 0.21% - 1.3% ,
VIII (8) - 1800 - 178200 - 1247400 - 0.22% - 1.52% ,
IX (9) - 1900 - 188100 - 1435500 - 0.23% - 1.75% ,X (10) - 2000 - 198000 - 1633500 - 0.24% - 1.99% ,
XI (11) - 2600 - 257400 - 1890900 - 0.31% - 2.3% , *
XII (12) - 3200 - 316800 - 2207700 - 0.39% - 2.69% ,
XIII (13) - 3800 - 376200 - 2583900 - 0.46% - 3.15% ,
XIV (14) - 4400 - 435600 - 3019500 - 0.53% - 3.68% ,
XV (15) - 5000 - 495000 - 3514500 - 0.6% - 4.28% ,
XVI (16) - 7000 - 693000 - 4207500 - 0.84% - 5.13% , *
XVII (17) - 9000 - 891000 - 5098500 - 1.09% - 6.21% ,
XVIII (18) - 11000 - 1089000 - 6187500 - 1.33% - 7.54% ,
XIX (19) - 13000 - 1287000 - 7474500 - 1.57% - 9.11% ,
XX (20) - 15000 - 1485000 - 8959500 - 1.81% - 10.92% ,
XXI (21) - 15400 - 1524600 - 10484100 - 1.86% - 12.77% , *
XXII (22) - 15800 - 1564200 - 12048300 - 1.91% - 14.68% ,
XXIII (23) - 16200 - 1603800 - 13652100 - 1.95% - 16.63% ,
XXIV (24) - 16600 - 1643400 - 15295500 - 2% - 18.64% ,
XXV (25) - 17000 - 1683000 - 16978500 - 2.05% - 20.69% ,
XXVI (26) - 17400 - 1722600 - 18701100 - 2.1% - 22.79% ,
XXVII (27) - 17800 - 1762200 - 20463300 - 2.15% - 24.93% ,
XXVIII (28) - 18200 - 1801800 - 22265100 - 2.2% - 27.13% ,
XXIX (29) - 18600 - 1841400 - 24106500 - 2.24% - 29.37% ,
XXX (30) - 19000 - 1881000 - 25987500 - 2.29% - 31.66% ,
XXXI (31) - 19800 - 1960200 - 27947700 - 2.39% - 34.05% , *
XXXII (32) - 20600 - 2039400 - 29987100 - 2.48% - 36.54% ,
XXXIII (33) - 21400 - 2118600 - 32105700 - 2.58% - 39.12% ,
XXXIV (34) - 22200 - 2197800 - 34303500 - 2.68% - 41.8% ,
XXXV (35) - 23000 - 2277000 - 36580500 - 2.77% - 44.57% ,
XXXVI (36) - 23800 - 2356200 - 38936700 - 2.87% - 47.44% ,
XXXVII (37) - 24600 - 2435400 - 41372100 - 2.97% - 50.41% ,
XXXVIII (38) - 25400 - 2514600 - 43886700 - 3.06% - 53.47% ,
XXXIX (39) - 26200 - 2593800 - 46480500 - 3.16% - 56.63% ,
XL (40) - 27000 - 2673000 - 49153500 - 3.26% - 59.89% ,
XLI (41) - 28000 - 2772000 - 51925500 - 3.38% - 63.27% , *
XLII (42) - 29000 - 2871000 - 54796500 - 3.5% - 66.77% ,
XLIII (43) - 30000 - 2970000 - 57766500 - 3.62% - 70.39% ,
XLIV (44) - 31000 - 3069000 - 60835500 - 3.74% - 74.13% ,
XLV (45) - 32000 - 3168000 - 64003500 - 3.86% - 77.99% ,
XLVI (46) - 33500 - 3316500 - 67320000 - 4.04% - 82.03% , *
XLVII (47) - 35000 - 3465000 - 70785000 - 4.22% - 86.25% ,
XLVIII (48) - 36500 - 3613500 - 74398500 - 4.4% - 90.65% ,
XLIX (49) - 38000 - 3762000 - 78160500 - 4.58% - 95.24% ,
L (50) - 39500 - 3910500 - 82071000 - 4.76% - 100%
How can you boost this?
There were different methods in the past but most of them got patched (idle boosting and ribbon boosting). There is only one decent method left. You can do this on any map but most of the people do this on two maps.
Load up "The Mines" on Inconceivable. Kill the first juvie/reject for the "first ribbon". Press "start" -> "restart act". Before the game is reloading press "start" -> "return to lobby".
You will get about 3000xp (1600xp if you don't have boost).
NOTE: You do this on "Inconceivable" that you can get rid of the Ironman mutator
Second map is "The Descent". One of the latest patches removed the ironman ribbon. So you can do the same method on "Master" difficulty. You will get about 3200xp with boost. However you have to walk a little bit further and it is a little bit harder to kill one enemy.
Doing this on the PC can save some time. My PC is more than 1 minute faster compared to an XBOX One X per run.
You are wrong if you think you get a decent reward for your re-ups by the way.
Re-Up Rewards
1. 1st Blood Spray
2. Desert Camo Talon
3. Desert Camo Enforcer
4. Desert Camo Retro Lancer
5. Desert Camo Snub
6. Desert Camo Markza
7. Desert Camo Dropshot
8. Desert Camo Overkill
9. Desert Camo Lancer
10. Desert Camo EMBAR
11. Desert Camo Lancer GL
12. Desert Camo Boomshot
13. Desert Camo Breaker Mace
14. Desert Camo Longshot
15. Desert Camo Hammerburst
16. Desert Camo Boltok
17. Desert Camo Torque Bow
18. Desert Camo Claw
19. Art Deco Retro Lancer
20. Desert Camo Gnasher
21. Get Some! Talon
22. Get Some! Hammerburst
23. Get Some! Enforcer
24. Get Some! Retro Lancer
25. Get Some! Snub
26. Get Some! Markza
27. Get Some! Dropshot
28. Get Some! Overkill
29. Get Some! EMBAR
30. Get Some Boomshot
31. Get Some! Lancer
32. Get Some! Breaker Mace
33. Get Some! Longshot
34. Get Some! Lancer GL
35. Get Some! Boltok
36. Get Some! Torque Bow
37. Get Some! Claw
38. Get Some! Gnasher
39. Team Ice Enforcer
40. Team Ice Breaker Mace
41. Team Ice Markza
42. Team Ice Dropshot
43. Team Ice Overkill
44. Team Ice Boomshot
45. Team Ice Torque Bow
46. Team Ice Claw
47. Team Ice Boltok + Team Ice Talon
48. Team Ice Longshot + Team Ice EMBAR
49. Team Ice Lancer GL + Team Ice Retro Lancer + Team Ice Hammerburst
50. Team Ice Lancer + Team Ice Gnasher + Team Ice Snub
Source:
https://forums.gearsofwar.com/t/world-first-re-up-50s-re-up-...