You can't really say what's the best because every weapon in that game is just unique in it's own way, which is why the game is awesome! For example if you like to be in mid-range and your aim is on point, FAMAS is great. If you like rushing in like a maniac M4 and AK are great. But if you like long range you got the FAL and ODEN. Like I said, it really depends on your preference and aiming. I hate SCAR for example because of the ammo capacity but a lot of my friends love it
For multiplayer - M4A1, AK (for long range headshots), MP5 - spec for fast ADS
For warzone - M4A1 with the grenadier barrel, MP7 - spec for long range accuracy and get bigger magazines
For me the oden is a very good damaging weapon if you have some aim. It can probably 1 shot someone in the head. It acts like a semi auto sniper but it's actually automatic.