I won't share my Suicune's super private EV spread here 
but i can share the one i'm not using anymore. It's still a good build, made to achieve some important goals while being a bulky support.
Suicune @ Sitrus Berry
Ability: Pressure
Level: 50
EVs: 252 HP / 116 Def / 116 SpA / 4 SpD / 20 Spe
Modest Nature
- Scald
- Ice Beam
- Tailwind
- Snarl
20 Spe EVs let you outspeed an Adamant ScarfLand-T after a Tailwind and OHKO it with Ice Beam. 116 SpA to OHKO M-Mence too. 252 HP EVs are really important, while 116 Def are put here to take some strong physical attacks you have to endure to set up a Tailwind in the first round.
116+ SpA Suicune Ice Beam vs. 4 HP / 0 SpD Mega Salamence: 172-204 (100.5 - 119.2%) -- guaranteed OHKO
116+ SpA Suicune Ice Beam vs. 4 HP / 0 SpD Landorus-T: 188-224 (113.9 - 135.7%) -- guaranteed OHKO
252+ Atk Parental Bond Mega Kangaskhan Double-Edge vs. 252 HP / 116 Def Suicune: 132-157 (63.7 - 75.8%) -- guaranteed 2HKO
252 Atk Aerilate Mega Salamence Double-Edge vs. 252 HP / 116 Def Suicune: 117-138 (56.5 - 66.6%) -- guaranteed 2HKO
However those 116 Def can be split into both Def and SpD as you like. I'm saying this because Suicune's only weaknesses are Electric and Grass types, that are usually special moves.
@Edit: 20 Spe EVs let you outspeed a 4 Spe Rotom-W too, that is great to set up a Tailwind before the opponent can actually double target you.
but i can share the one i'm not using anymore. It's still a good build, made to achieve some important goals while being a bulky support.Suicune @ Sitrus Berry
Ability: Pressure
Level: 50
EVs: 252 HP / 116 Def / 116 SpA / 4 SpD / 20 Spe
Modest Nature
- Scald
- Ice Beam
- Tailwind
- Snarl
20 Spe EVs let you outspeed an Adamant ScarfLand-T after a Tailwind and OHKO it with Ice Beam. 116 SpA to OHKO M-Mence too. 252 HP EVs are really important, while 116 Def are put here to take some strong physical attacks you have to endure to set up a Tailwind in the first round.
116+ SpA Suicune Ice Beam vs. 4 HP / 0 SpD Mega Salamence: 172-204 (100.5 - 119.2%) -- guaranteed OHKO
116+ SpA Suicune Ice Beam vs. 4 HP / 0 SpD Landorus-T: 188-224 (113.9 - 135.7%) -- guaranteed OHKO
252+ Atk Parental Bond Mega Kangaskhan Double-Edge vs. 252 HP / 116 Def Suicune: 132-157 (63.7 - 75.8%) -- guaranteed 2HKO
252 Atk Aerilate Mega Salamence Double-Edge vs. 252 HP / 116 Def Suicune: 117-138 (56.5 - 66.6%) -- guaranteed 2HKO
However those 116 Def can be split into both Def and SpD as you like. I'm saying this because Suicune's only weaknesses are Electric and Grass types, that are usually special moves.
@Edit: 20 Spe EVs let you outspeed a 4 Spe Rotom-W too, that is great to set up a Tailwind before the opponent can actually double target you.
