A player who has ten or more poison counters loses the game. This is a state-based action.

Infect's effect applies to any damage, not just combat damage.

The -1/-1 counters remain on the creature indefinitely. They're not removed if the creature regenerates or the turn ends.

Damage from a source with infect is damage in all respects. If the source with infect also has lifelink, damage dealt by that source also causes its controller to gain that much life. Damage from a source with infect can be prevented or redirected. Abilities that trigger on damage being dealt will trigger if a source with infect deals damage, if appropriate.

If damage from a source with infect that would be dealt to a player is prevented, that player doesn't get poison counters. If damage from a source with infect that would be dealt to a creature is prevented, that creature doesn't get -1/-1 counters.

Damage from a source with infect affects planeswalkers normally.

You may activate Tangle Angler's second ability multiple times in a turn to force multiple creatures to block it.

Activating Tangle Angler's second ability doesn't force you to attack with Tangle Angler that turn. If it doesn't attack, the targeted creature is free to block whichever creature its controller chooses, or block no creatures at all.

If you attack with Tangle Angler but a creature you targeted with its activated ability isn't able to block it (for example, because an effect has granted Tangle Angler intimidate and the other creature is white), the other creature is free to block whichever creature its controller chooses, or block no creatures at all.

Tapped creatures, creatures that can't block as the result of an effect, creatures with unpaid costs to block (such as those from War Cadence), and creatures that aren't controlled by the defending player are exempt from effects that would require them to block. Such creatures can be targeted by Tangle Angler's activated ability, but the requirement to block does nothing.