Here is the full list of all 70 Serious Sam HD: The Second Encounter achievements.
Frag 100 different players.
Win 1000 Deathmatch games.
Frag a total of 1337 players.
Win 100 Instant Kill matches.
Win 100 Team Deathmatches with at least 2 players on each team.
Frag a total of 1000 players.
Win 100 My Burden matches with at least 3 players.
Hold the Burden for at least 10 minutes in My Burden match with at least 3 players.
Win 100 Last Team Standing matches with at least 2 players on each team.
Frag 10 players without being killed in at least 4 player Instant Kill match.
Earn a round for your team in Last Team Standing game with at least 2 players on each team.
Win a Team Beast Hunt match on all game levels with least 2 players on each team.
Win an at least 4 player Deathmatch by reaching frag limit of at least 25 without dying.
Frag the same player 5 times in a row in at least 4 player match.
Perform 4 frags with each being no more than 10 seconds apart from the previous frag in at least 4 player Deathmatch.
Frag all players in a single frag combo.
Win one Team Deathmatch with at least 2 players on each team.
Win a Beast Hunt match on all game levels.
Win one My Burden match with at least 3 players.
Earn gold medals on all Survival levels in cooperative Survival.
Win a Team Beast Hunt match on any level with least 2 players on each team.
Frag 25 players with a knife while having no more than 10 health left.
Win 100 Last Man Standing matches with at least 4 players.
Win one round in Last Man Standing game with at least 4 players.
Win 25 CTF matches with at least 2 players on each team.
Make at least 3 kills in one Instant Kill match.
Win a CTF match with at least 2 players on each team.
Win a Beast Hunt match on any level.
Frag 100 players in a knife-to-knife fight.
Frag 100 players with a knife from behind.
Frag 100 players with a knife.
Complete a Coin-op cooperative game on normal or higher difficulty.
Pick up 100 gold coins in Coin-op Cooperative game.
Pick up at least 10 extra life items in Cooperative Coin-op game.
Complete any level in at least 3 player cooperative game.
Earn at least a bronze medal on any level in cooperative Survival.
Frag a total of 500 players.
Earn gold medals on all Survival levels in single player Survival.
Win 100 deathmatch games.
Complete 100 Deathmatches.
Win 25 1-on-1 Deathmatches.
Complete a deathmatch game with at least 1 frag.
Frag the same player 10 times during a single round in at least 4 player match.
Frag a total of 100 players.
Win a Deathmatch.
Complete a Deathmatch with frag limit set to at least 200. (Frag limit must be reached!)
Win a Deathmatch Marathon.
Earn at least a bronze medal on any level in single player Survival.
Kill 1000 enemies with the Laser gun.
Kill 100 Harpies with the Sniper rifle.
Accumulate a total of 100,001 enemy kills and frags combined.
Kill 50 Syrian Werebulls with a knife.
Complete The Grand Cathedral level on serious difficulty without dying or loading.
Complete the game.
Complete the game in single player on serious difficulty.
Complete the game in single player by beating estimated time on each level.
Complete the Medieval episode in single player or cooperative.
Find all secrets in single player.
Deliver the final blow to Mordekai with the Knife.
Perform 100 rocket jumps.
Complete the Persia episode in single player or cooperative.
Score a total of 100 points in CTF matches.
Kill 300 Kleers with the Cannon.
Find at least 80 secrets in single player.
Complete the South America episode in single player or cooperative.
Burn 500 enemies to death.
Find all 3 Cannons in Teotihuacan - The City of the Gods.
Complete any level in single player.
Get all 3 Rocket launchers in Palenque - Sierra de Chiapas.
Find a secret under water.