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